Mars is extraordinarily cold and dry, like our most arid deserts. Harsh but possibly not totally lifeless. There is a chance of life there, hidden away perhaps in thin layers of brines just a couple of centimeters below the surface, or as spores within the dust. Our astronauts will be covered in microbes from Earth too and our habitats filled with life. What happens when life mixes together from these two biospheres? This might be their first meeting for billions of years, or the first time ever, as astrobiologists haven't yet ruled out the possibility that Martian life is independently evolved. And if the more optimistic projections of Elon Musk, some NASA enthusiasts, and Bill Nye and others are fulfilled, then this encounter may happen as soon as the 2030s, perhaps sooner. Are we ready for it?

We might get on wonderfully well with our microbial interplanetary neighbours. But there again we might not. Legionella bacteria for instance grow in biofilms and also in our lungs causing Legionnaires' disease. Blue green algae sometimes form greenish patches that cover our lakes and the sea. They produce toxins that are probably targeted at other tiny creatures in our seas and lakes, but still sometimes kill cows and dogs, rapidly, in hours, by destroying their livers. Sudden deaths after nibbling at algal blooms washed onto the shore.

We need to know the answer to this, and until then, we have to protect Earth from Martian microbes. NASA hope to return small samples from Mars in the 2030s. But we are no longer back in the naive days of Apollo when there was little public awareness of the need to protect Earth's environment. Numerous laws have been passed since then, and they can't be ignored. I've suggested that once they start on the legal process and discover how much is involved, they are likely to take the easy way out and return it to somewhere that requires no extra laws to be passed, say, to above Geostationary Orbit, or sterilize the samples before returning them to Earth.

If it's so hard to return a sample of rock by 2040, what about an astronaut who has landed on Mars, and got covered in Martian dust? How could we prevent any Martian life in the dust from finding its way back to Earth at the end of the mission?

The keenest Mars colonization enthusiasts sometimes argue that we don't need to take any precautions at all. But their arguments are not accepted by planetary protection experts.

Indeed the expert reports, and there have been many, all say that we need to protect Earth's environment from native life returned from Mars. See for instance the study by the European Space Foundation: (Mars Sample Return backward contamination – Strategic advice and requirements) and a similar one by the NRC of the USA (Assessment of Planetary Protection Requirements for Mars Sample Return Missions). Those warnings would not be ignored as we work through the laws that protect Earth's environment.

The answer to all this is to find out a little about our microbial neighbours before planning an exchange visit of this sort. However, we haven't started on this yet. We've sent many missions since the Viking landers in the 1970s, but they were all searching for habitability, not life. 

So, how should we do this survey? Why would we do it from orbit? And might that even be required by the laws to protect Earth? 

Let’s investigate.

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So, why would we want to explore Mars from orbit anyway, rather than do it from the surface? One reason is because we want to find native Martian life, rather than the microbes we bring ourselves.

Human bodies are wonderful microbe incubators, with ten to a hundred billion foreign microbes on our skin, and it takes only a month from when a cell is born in the basal layer to when it is shed, carrying any foreign microbes away with it. That’s right, the entire surface of our skin is slowly shed, flake by flake, around once a month. Every single second we emit larger biological particles by the tens of thousands, and tiny sub micron ones by the hundreds of thousands (see figure 7 of this paper). These constantly carry our tiny passengers away into the air around us in our personal microbial clouds.

(Click to watch on YouTube)

The last thing we want to do is to go to another planet, and search for life, just to find these microbial passengers that we are constantly emitting. This doesn’t matter so much for most researches on Earth, although in the McMurdo dry valleys in Antarctica they do take precautions to keep our microbes within a “corral” around the researchers’ tents (see Non-indigenous microorganisms in the Antarctic: Assessing the risks). But on Mars, discovery of a few amino acids or a single microbial spore, even a dormant or dead spore, could lead to a revolution in astrobiology.

What’s more, the Martian surface has turned out to be more habitable than we realized just a decade ago. There may well be thin layers of salty water that Earth life could live in, just a couple of centimeters below the surface, and there are several other possible habitats.

So what can we do about this? One approach is to keep our astronauts in orbit as they control sterile rovers on the surface, much like the way players use 3D virtual reality to control avatars in a computer game. Emily Lakdawalla of the Planetary Society once put it like this:

“But all bets are off once you send humans to Mars. There is absolutely no way to make a human clean of microbes. We are filthy with microbes, thousands and thousands of different species. We continuously shed them through every pore, every orifice, with every exhalation, and from every surface. True, almost all of our microscopic friends would fail to thrive in the radiation-baked, intensely cold and arid Martian environment. But life is incredibly tenacious. Sooner or later, humans will get to Mars; even if they die in the attempt, some of their microbial passengers will survive even the worst crash. Once we've put humans on the surface, alive or dead, it becomes much, much harder to identify native Martian life.”

“If we keep our filthy meatbag bodies in space and tele-operate sterile robots on the surface, we'll avoid irreversible contamination of Mars -- and obfuscation of the answer to the question of whether we're alone in the solar system -- for a little while longer. Maybe just long enough for robots to taste Martian water or discover Martian life.”

From: NASA's Mars Announcement: Present-day transient flows of briny water on steep slopes (emphasis mine)

From our Mars simulation experiments, many Earth extremophiles can tolerate Martian conditions. I give a list of some of the top candidates so far here, "Candidate lifeforms for Mars" in an article I contributed to Wikipedia on Modern Mars Habitability.

In the very worst case, but exceptionally interesting of some early form of life on Mars, we could even lose all Martian life rapidly, as soon as Earth life encounters its habitats.

  • Pre-Darwinian life. Carl Woese's theory. He thinks early life evolved through massively parallel evolution through cells that share RNA through the cell walls. The RNA evolves, the cells develop new capabilities, however they share these capabilities with all the other cells in the biofilm. There is no interspecies competition yet and no predation. Just horizontal gene transfer. A kind of Lamarckian, soft inheritance, but also, a communal inheritance with all capabilities shared with any cells that need them. Our Earth life, could spread through it like a Petri dish, munching up everything as it goes (worst case, extinct).
  • RNA world cells (one of the suggestions for the tiny structures in the Martian meteorite ALH84001) - easy to identify before Earth life is introduced as there is no DNA at all in the habitat. Introduce Earth life and it may be hard to spot that there is any RNA world lilfe there at all, rather than an unfamiliar form of DNA based life. And - there is no RNA world life left on Earth as far as we know. DNA based life might do whatever it is it did to make it extinct on Earth- or whatever was our precursor lifeform here. Life based on DNA is far too complex to have been the earliest form of life (confuses science, may go extinct).
  • Distant cousin based on DNA,  well every survey of clean room spacecraft surfaces finds new DNA sequences, and we discover entire new phyla of archaea often too, we only have estimates of the total number of phyla, and if we find a new microbe on Mars, even as distantly related to known Earth life as fungi and plants, or more so, there would be no way to know if it is native or from Earth. Only 0.00001% of the estimated trillion microbe species have been sequenced (unless already sequenced, won't be able to tell if it came from Earth or not)

For more on this see Worst case from Earth to Mars - Carl Woese's pre LUCA non Darwinian life -before predation or interspecies competition (below),

However it’s not just the native life on Mars that needs planetary protection; to avoid confusing our experiments. We on Earth need protection too, in the other direction, from Martian microbes. There have been several detailed reviews, including ones by the National Research Council in the US and the European Science Foundation, and they are all in agreement that we need to protect Earth. Not only from microbes that could harm our astronauts or ourselves. The Outer Space Treaty actually refers to "adverse changes in the environment of the Earth". Microbes harmless to us could potentially change the environment, or harm other living creatures in our biosphere. This could be like that example of blue green algae harming dogs and cows, for a simple example, but it could potentially happen on a larger scale. See Worst case from Mars to Earth - Joshua Lederberg's example, Martian life has a field day, because of total naivete of Earth life never exposed to anything like it before (below)

That’s another reason for our astronauts to explore Mars from orbit. There is no way for any Martian life to get into their spaceship, or back to Earth. This gives us complete protection, as we continue to search for it on Mars, and evaluate its capabilities.

You will sometimes hear colonization enthusiasts say that we don’t need any protection, because Earth gets meteorites from Mars all the time. The idea is that any life on Mars must have got here already. I looked at this in my last article, and we will look at it in a little more detail later in this article too. Meanwhile here is a short summary:

Yes, part of that is true, we get tons of meteorites from Mars a century. However, these meteorites traveled through interplanetary space for between 600,000 years and twenty million years and are thoroughly sterilized by ionizing radiation. The most recent time that viable life could get to us from Mars on these meteorites was three ice ages ago, but this was after a glancing impact on the high southern uplands, where the atmosphere is thin. Those rocks also came from at least 3 meters below the surface, where its extremely cold and dry even for Mars. As it turns out, it’s the same story for all the impacts that sent rocks our way for the last twenty million years.

Perhaps life got to Earth more than twenty million years ago? If so, who is to say it didn’t cause mass extinctions? The NRC sample return study looked into this. Many of them are not yet fully understood, and we can’t rule out the possibility of mass extinctions due to Martian life.

Or perhaps it never got here at all? We have no idea what capabilities Martian life has. But a microbe on Mars doesn’t need to be able to survive the shock of being knocked off Mars by an asteroid, the long journey to Earth through a hard vacuum, and entry into our atmosphere, with a layer of the surface of the rock centimeters thick ablated away in a fireball, to be a nuisance in our biosphere.

Exploration from orbit is undoubtedly safest for Earth (you can’t get better than no risk at all). It also provides better protection of Mars in the forwards direction.

You might think that this is a painfully slow way to do the search. Wouldn’t it be far faster to land our astronauts on the surface? Some would say that the safety of Earth’s environment is of utmost importance - as is the importance of preserving the science value of what we could find on Mars, at least until we know what we might lose. They would say that we have to take as long as is required to do the search properly (I’m of that view myself). But actually, if you look at it closer, the search from orbit might be faster than you expect. It may indeed be faster to have the astronauts in orbit than on the surface.

There are some significant downsides to surface explorations. You are limited to exploring a small region around your landing site. Your spacesuits are also awkward to use at present, the gloves are particularly stiff (like having your fingers inside a garden hose) because of the pressure difference, and it takes a fair amount of time to maintain them and don and doff them each day if you do all the safety checks. And there, I mean hours, not minutes. They are as complex as miniature spaceships, need a lot of maintenance (hours for each EVA at present) and need to be replaced or refurbished regularly (returned to Earth every 25 EVA's for the US EMU and discarded after 12 EVA's for the Russian Orlon). On Mars, they have to cope with the Martian dust, and astronauts stumbling and falling. Some Apollo suits were so damaged by three EVA's that they were not cleared as safe for the fourth in orbit EVA to retrieve the external lunar module camera.  If your spacesuit is damaged to the point where you can no longer do a safe EVA, then you can no longer leave your habitat. Note, these are not to be confused with the much simpler IVA’s you often see in promotional shots for space tourism, which are designed only to protect the inhabitants for a short while after an emergency depressurization. For more on this see Why it’s a big deal that telerobotic astronauts do not need to suit up for an EVA (below).

The only comparison study I know of, HERRO, found that a mission by a crew of six in orbit around Mars, teleoperating rovers on the surface, does as much science as three missions of the same size to the surface for far less cost. They also found that they can use their telerobots to explore anywhere on Mars, including the hard to access polar regions. These regions of Mars are not likely to see a human landing for a long time, because of long continuous periods of darkness, and a thick extra layer of dry ice every winter. HERRO’s carefully chosen orbit lets the astronauts tele-operate rovers over the entire surface of Mars with almost no time delay, for hours at a time for each location (it skims the sunlit side of Mars twice a day every Martian day, visiting opposite hemispheres, always in sunshine, and flies close to both poles twice a day too, giving global coverage).

Image: A teleoperated Centaur-style robot on Mars. Carter Emmart/NASA Ames Research Center - from Almost Being There: Why the Future of Space Exploration Is Not What You Think

This shows how you get into this orbit - just directly from the Earth-Mars transfer orbit.

Note the light speed time delay is minimal. The Moon is 1.3 light seconds away and so telepresence of robots on the Moon from Earth would require ways to handle a large time delay (which is not impossible, after all with 1970s technology the Russians drove Voskhod 2 in a few months as far as Opportunity drove in a decade).

But with Mars it is far better. Phobos is only 0.03 light seconds away from Mars, 0.06 seconds round trip. In the HERRO orbit they can come even closer. Both of these are close enough to not notice the light speed time delay. For full haptic (touch) control you need 0.1 seconds. You can go up to 0.2 seconds for visual control - so they are well within this and you wouldn't notice a delay even handling things by touch. You'd be able to do haptic feedback not just when close to Mars but up to 15,000 km away and visual feedback up to 30,000 km without noticing it. The crew do the telepresence during eight hours of each twelve hour orbit when close to Mars giving two eight hour shifts for opposite sides of Mars in sunlight every 24 hours. It gives much more telepresence time than Phobos where you have continuous telepresence for 4 hours and it's hard to explore polar regions (without relaying satellites). For details: HERRO Mission to Mars Using TeleroboticSurface Exploration From Orbit. Russia suggested a similar mission as an international effort, with US participation for the teleoperated landers, called the Mars Piloted Orbital Station.

Their result may surprise you, used to the slow pace of our Martian rovers Opportunity and Curiosity. These can spend days to do an experiment or to return a multi-frame panorama. An astronaut on the surface could do the same things in minutes, even in a spacesuit.

However a lot of that difference arises because our rovers travel so slowly, and send data back so slowly too.

  • They have a top speed of 100 meters a day, roughly the same as a garden snail.
  • They also manage a maximum of a few minutes of data transfer back to Earth a day.
  • Typically the operators communicate with the rovers only once a day (they could be as far away as Sedna, a distant ice dwarf way beyond Neptune, and the operators on Earth would hardly notice any difference).

Future Martian high powered semi-autonomous robotic rovers could be

  • As fast as the lunar rovers, or faster and travel hundreds of kilometers a day,
  • Relaying back continuous high bandwidth, 3D multigigabyte landscapes as they travel. Our astronauts in orbit around Mars, and indeed scientists back on Earth, and anyone else, could explore these landscapes at our leisure in 3D VR, even peering close up at the rocks, much as if they were there on the surface of Mars in person.
  • The astronauts in orbit can do fast on the spot decisions with low latency telepresence.

All of this speeds things up hugely, faster rovers, higher bandwidth, and continual on the spot executive decisions by humans.

And when it comes to astrobiology we are yet to send our first astrobiological instruments to Mars since Viking. Technology has moved on hugely since then of course. We could have entire biological laboratories of the 1970s vastly more capable, within the payload of Viking, capable of DNA sequencing which they couldn't even imagine doing back then, but many other things that to them would be almost magical in tiny instruments, labs on a chip, weighing kilograms at most, of exquisite sensitivity, and requiring only watts of power. Many of those have been developed, some close to flying, even space certified but descoped at the last minute. See How do we search for life from orbit? - The amazing advances in the technology for In situ biosignature detection instruments (below)

Far from reaching the limits of what we can do via rovers, as far as astrobiology is concerned, we haven't even started.

And yes, rovers can drill on Mars, using self hammering moles, and other techniques. Indeed the conditions are far from ideal for the drilling methods we are used to on Earth. I covered that in my last article under:

It's also good for human health. You can use a tether and a counterweight - perhaps the final stage for the mission - or perhaps you have two identical spacecraft (e.g. two BFR's) - which is also great for safety, tethered to each other and slowly spinning for full gravity. Or Martian gravity or anything in between as desired.

This approach is safe, practical, seems likely to do most science return for the least cost and also is the only reasonably sure way to protect both any native Martian life and the environment of Earth. It was highlighted in the NASA Telerobotics symposium for its planetary protection credentials, and as a fast effective way to do the science.

Telerobotics Could Help Humanity Explore Space Credit NASA / GSFC. "Safely tucked inside orbiting habitat, space explorers use telepresence to operate machinery on Mars, even lobbing a sample of the Red Planet to the outpost for detailed study." - I've added the HERRO image of a tele-operated Centaur as an insert.

The astrobiologists say we need to look for life in situ first, so that we can distinguish the organics that fall on Mars from space from any indigenous abiotic organics, and the probably faint and scattered traces from indigenous past or present day life. See How do we search for life from orbit? - The amazing advances in the technology for In situ biosignature detection instruments (below). So it might be a while before we need to return a sample for astrobiological study. Geological samples could be sterilized on the surface, perhaps with a portable gamma ray source, equivalent to a few million years of surface ionizing radiation (which would still preserve some of the organics, similarly to the organics in Martian meteorites).. As for biologically interesting samples, they could be returned to separate telerobotic facilities around Mars or Earth, or back to the habitat itself if by then they know enough to be sure that it is okay for humans and Earth to enter the chain of contact.

The artist's impression doesn't show an agricultural module - but for missions that last three years, it breaks even and for longer missions, it is well worth growing all your own food. For shorter missions you might as well take food supplies but have some supplementary fresh food for morale, and you can have algae for some food supplements, and to help with oxygen, especially perhaps as an emergency backup. If we are doing a telerobotic survey from orbit it's likely to take more than three years, so then it is worth taking an agricultural module, probably with light fed into it with light collectors - and eventually build up to a small settlement in orbit around Mars, or perhaps on one of its two moons.

A Lockheed-Martin study found that they could alternatively tele-operate rovers from a human base on Phobos or Deimos (which gives an opportunity to explore those moons too, including the regolith which has materials from impacts from Mars throughout its history mixed in the dirt). There’s no doubt about the science credentials of this approach as a good way to explore Mars.

The HERRO comparison was a small scale study and from nearly a decade ago. It would be good to have a more detailed study of the same sort, and based on the latest technology, but I think it is likely to come to the same conclusion, that it is faster for astronauts to explore Mars from orbit, for less cost, and with better science return. See the section Need for an updated comparison study (below)


Sometimes people will say that this is just not part of human nature, to orbit Mars but never land. Won't it be hard to recruit a crew for such a mission? However, the Apollo 10 astronauts went to the Moon, flew around it many times, undocked, flew all the way down to the surface just short of a landing, and then returned to orbit. In the process they turned up a bug that could have killed them all if they had landed. People are able to orbit and not land even with the capability to do so, if that is what the situation indicates. And of course in each Apollo mission the command module pilot remained in orbit while his two companions were on the surface. That was the same situation, flew all the way to the Moon, orbited it several times, his companions landed but he didn't and then he returns to Earth. No complaints about this from Michael Collins, command module pilot for Apollo 11 :). He enjoyed his quiet time in orbit especially when he was on the far side of the Moon cut off from mission control for about 55 minutes at a time.

(Click to watch on YouTube)

In the case of a Mars telerobotic orbital mission, to know that landing would potentially risk harm to Earth or make native Martian life extinct is a significant downside. And for a years long mission to Mars we are not talking about foolhardy people who jump into some activity without thinking about it first.

The telerobotic mission is an interesting and satisfying mission for highly trained and disciplined astronauts exploring Mars. They don't land in person, true, but their minds are there on the surface, exploring the surface. Indeed, they have a more direct experience in some ways, not encumbered by clumsy spacesuits. For an astronaut's reaction, here is Eileen Collins response to a question - would she be disappointed if she was selected for a mission to Phobos instead of Mars. See 35 minutes into this SpaceShow talk. Like many astronauts she has a military background and approaches this as an officer would, given a new duty. So long as the decision is made in the right way by a group of knowledgeable people, and it is done in the open, all know that it is the right thing to do, she would not be disappointed. Would be very honoured and excited to carry forward the space program wherever it goes. Do listen to what she says, it's interesting to get the astronaut's perspective on such a mission as a former NASA astronaut, also a military instructor and a test pilot.

Tom Jones similarly, again with a military background and a former astronaut, says he used to say he wouldn't go - but if it is part of progress, in space, and if asked to land on Phobos, build facilities there, that would be fascinating. He wouldn't want to sit in an orbiting laboratory for months around Mars - unless you could let him put his mind on the surface and operate rovers in real time from orbit. He thinks that's an intriguing concept. It could put your mind every day at work on the surface without exposing you to some of its hazards. 29 minutes into this Space Show talk.

I think it might help if it's a spectacular orbit like the HERRO one, zooming in close past the ice caps and the entire surface of Mars pretty much from North to South at low altitude twice a day - then so far out again that it becomes like a distant small planet. I think it would take a long time before you were bored gazing out at that sight, it would be like astronauts in the Cupola of the ISS. See The spectacular HERRO telerobotics orbit . Or a mission on the Martian moons, actually quite large. Phobos has a surface area of 1548.3 km². That's the same area as a region 40 km by 40 km - there's a fair amount to discover there, and all the time you are also (to use Tom Jones's phrase) putting your mind on the Martian surface every day for hours at a time as part of your job, exploring it via telepresence.

Incidentally, NASA, Lockheed Martin, the Planetary society and Russia have all proposed sending telerobotic explorations to Mars first before landing there. That's not much different from Apollo where we had Apollo 8 and Apollo 10 that orbited it without landing. The main difference here is that this would not be a single mission, but as much by way of orbiting missions as is necessary to complete a reasonable astrobiological survey of the planet. The astronauts would understand why they are doing this, that it's an important job that is done this way from necessity and to protect Earth, themselves, and the science interest of Mars.

If you need a symbolic "flag and footprints" for the photo op - why not a cute sterilized Asimo miniature robot, with boots that have real treads like a normal astronaut and teloperate it from orbit to put a symbolic flag into the Martian dust?

However, in the intro to this article, I went much further than saying it is good science to do things this way, or that it costs less or is faster, or safer. I asked if this is likely to be REQUIRED under our laws to protect Earth’s environment.

I’m talking about our existing laws there, not proposals for future laws. I will suggest that it may already be a requirement to do it this way, at least for most missions we are likely to want to do, due to laws we didn’t have at the time of Apollo, and that can’t be ignored.

How can that be?

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How to read this off-line

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Next section: How astronauts returning from Mars will mean we need to protect Earth



Let’s see if you agree. It is all to do with what happens when the astronauts get back to Earth. Only “Mars One” propose a one way “to Mars and die there” mission, and hardly anyone takes them seriously. The others all envision the astronauts returning. Indeed the first missions would probably only last a year or so on Mars, preparing for future longer duration follow up missions.

The problems start when an astronaut on one of these missions becomes part of the “chain of contact” with Martian materials, because that gives a way for any hardy Martian microbial spores to get back to Earth. Now, you might think, how can our astronauts contact the surface, in a spacesuit? You can’t touch the soil or rocks yourself; only through spacesuit gloves.

Well the Apollo lunar astronauts showed vividly how this can happen, when they got covered in fine clinging dust during their EVA’s on the lunar surface. Gene Cernan got particularly dirty in this way, due to an incident with a broken fender, but they all got covered in dust.

Gene Cernan covered in dust on the lunar surface. How did he get like that? He accidentally snapped off a fender on the lunar rover with the result that it sprayed “rooster tails” of dust all over him. He fixed it with duct tape, but that didn’t last long, and it came off again. Eventually they fixed it more permanently with duct tape this time reinforced with curled up maps. See Duct Tape Auto Repair on the Moon

Here he is inside the lunar module.

And later once he took off his spacesuit:

Mars has dust as well, and the dust there is particularly fine, as fine as cigarette ash. Its winds loft clouds of this fine dust high into the atmosphere; dust clouds so thick that they can block out 99% of direct sunlight at times.

Although its winds are fast, its atmosphere is so thin that the strongest winds are barely strong enough to stir an autumn leaf. The astronauts would disturb the dust there more than any storm has ever done for millions of years. They would kick up huge clouds of fine dust wherever they walk, as much so as for the moon, and more so.

Also, the lunar astronauts had it easy in a way. The moon has no atmosphere and the dust flew in ballistic trajectories like kicking a stone. All they had to do is to get out of the way of the “rooster tails” of dust.

On Mars, the rovers would throw up clouds of dust, as well as the rooster tails, and the finest dust would remain suspended in the atmosphere for some time after the rover, or an astronaut passes by. They would be like the motes you see drifting, lit up by gleams of sunlight in a dusty room, but much smaller, too small to see individually.

(Click to watch on YouTube)

Then there are the dust devils, swirling mini tornadoes, that frequently pass by; and the dust storms themselves, sometimes thinner, sometimes thicker, and sometimes so thick they block out the sun for weeks on end.

(Click to watch on YouTube)

There are large quantities of fine dust in the Martian atmosphere all the time, even when it seems clear. This is what causes the blue sunsets and sunrises.

Curiosity photographed this sunset from Gale Crater on April 15, 2015. The sequence spans 6 minutes 51 seconds, using the leftmost camera of its Mastcam. The sunset is blue because the fine dust that’s always suspended in the Martian atmosphere absorbs red light. Credit: NASA/JPL-Caltech What Makes Mars Sunsets Different from Earth's? - Universe Today

One way or another, if there are any spores in the Martian dust, they will get into the air of their habitat, into their water, over the interior surfaces of the spacecraft, into their clothes, everywhere. All those surfaces are covered in spores of Earth life too, of course, so as they are spread around you will end up with potentially a few spores of Martian life mixed up with Earth life throughout the habitat.

It needn’t be spores only. Some of the Martian life might start to reproduce on our skin, on surfaces in the habitats, in the droplets of moisture we breathe out into the air, in our greenhouses (if they grow their own food), in our water, food, in our eyes, mouths, lungs, stomachs, and scavenging on flakes of skin and hair, and so on, just as thousands of species of Earth microbes of numerous types do. The Martian microbes might join the communities in our personal microbial clouds. They might also take their place in biofilms inside the habitats alongside Earth microbes.They are likely to start to carve out microhabitats for themselves, either competing with or predating on, or co-existing symbiotically with Earth microbes. Just as we are wonderful incubators for Earth microbes, there is nothing to stop us becoming incubators for Martian life too.

Just as with a robotic sample return, this makes the astronauts part of the chain of contact. But more so as the spores need not remain in a dormant state on humans.

For as long as it is necessary to protect the environment of Earth, we have to contain any spores that have got into the habitats of our Martian astronauts.

At least, if we want to protect Earth’s environment.

Okay - but perhaps you think this is an unlikely scenario. Could Earth’s environment really be endangered by microbes from another biosphere on Mars? It may sound like a plot-line for a science fiction movie. But do bear in mind, astronauts landing on Mars sound like science fiction too.

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I’d better cover this right away as you may well have heard that Mars has to be sterile, because of the perchlorates, ionizing radiation, and the UV. The surface of Mars is extreme for sure, a tough place to live. But we have life in many extreme conditions on Earth too.

The perchlorates can be used by some microbes as food (strictly speaking, the oxidiser for their food) and is not especially hazardous for them. UV is just light, beyond violet in the visible spectrum, and as such can be shielded by a thin layer of dust, or a shadow, or partial shade. We also have high levels of UV, in high mountains or polar regions. Some microbes have special pigments to shield them against UV.

What the experts say about the ionizing radiation on Mars might seem a little paradoxical. They will assure you that the Martian dirt is totally sterilized of dormant life to a depth of 2 meters over a time period of less than a million years. Yet they also say that Curiosity found that the Mars surface ionizing radiation levels are equivalent to the interior of the ISS. That’s not even lethal to humans, and microbes won’t notice it. How can that be?

It’s to do with the rather surprising way exponentials work. Explanation indented.

Techy note: How can ionizing radiation can be lethal for dormant life over millennia yet harmless over decades? - let’s take a simple example.

Suppose that a microbe’s numbers are halved after a century of dormancy? Then after a thousand years it’s down to a thousandth of its original population (210 is 1,024, approximately 1,000), after two thousand years, it’s down to a millionth, after three thousand down to a billionth and so on.

Yet, from one year to the next, the numbers will be reduced by less than 0.07%.

That’s just the surprising way exponential decay works. In short, ionizing radiation is a total non issue for surface life on Mars. Indeed, the most ionizing radiation resistant life could repair thousands of years worth of DNA damage in a few hours of metabolism.

Yes, they thought the ionizing radiation would sterilize Mars totally to a depth of a couple of meters or more, back when they thought it had had no liquid water for hundreds of thousands of years. However, on a shorter timescale, there is no problem at all for life that’s living on the surface right now.

The conditions there are extreme for sure, for Earth life at least. But uninhabitable? The jury is out on that one at present. Mainly because we haven’t been able to examine any of the potential habitats close up or search for life there yet.

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Nobody can give you a calculated figure here. They can give their personal views on the matter however.

As an example of an optimistic, indeed enthusiastically optimistic astrobiologist, let's suggest Nilton Renno, top expert on Mars atmosphere and surface conditions, formerly PI of Phoenix lander and in charge of the Mars REMs weather station on Mars. He is impressed by the droplets that formed on the Phoenix legs - his mission remember - and he developed a theory confirmed in Mars simulation experiments that explains it as perchlorate salts lying on top of ice. He showed that if this ever happens on Mars, that the perchlorate salts get thrown up on top of ice, then droplets of liquid brine, can form in tens of minutes, and these are potentially habitable, tiny as they are, "Swimming pools for a bacteria" as he memorably put it.

This is striking as it could open large areas of Mars up as potential sites for microhabitats that life could exploit. The professor says

"If we have ice, and then the salt on top of the ice, in a few tens of minutes liquid water forms. Our measurements clearly indicate that. And it's really a proof that liquid water forms at the conditions of the Phoenix landing site when this salt is in contact with the ice.

"Based on the results of our experiment, we expect this soft ice that can liquefy perhaps a few days per year, perhaps a few hours a day, almost anywhere on Mars. So going from mid latitudes all the way to the polar regions.

" This is a small amount of liquid water. But for a bacteria, that would be a huge swimming pool - a little droplet of water is a huge amount of water for a bacteria. So, a small amount of water is enough for you to be able to create conditions for Mars to be habitable today'. And we believe this is possible in the shallow subsurface, and even the surface of the Mars polar region for a few hours per day during the spring."

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That's Nilton Renno, who lead the team of researchers. See also Martian salts must touch ice to make liquid water, study shows . He is a mainstream researcher in the field - a distinguished professor of atmospheric, oceanic and space sciences at Michigan University. For instance, amongst many honours, he received the 2013 NASA Group Achievement Award as member of the Curiosity Rover " for exceptional achievement defining the REMS scientific goals and requirements, developing the instrument suite and investigation, and operating REMS successfully on Mars" and has written many papers on topics such as possible habitats on the present day Mars surface.

He also wrote the main survey paper.on possibilities for liquid water on the surface of Mars, which turned up numerous research results by other authors, exploring various ideas some of which are barely known by anyone outside the specialist literature (I've tried to publicize some of them in my posts). He sees potential habitats just about anywhere on Mars for both native and introduced life. He also thinks this life can also modify those habitats as biofilms do to make them more habitable.

Then, in this optimistic group again, I'd add the astrobiologists at DLR (Germany's aerospace agency) who did some remarkable experiments in their Mars simulation chambers showing that modern polar lichens including one that survives at high altitudes in Antarctica can mange just fine in a Martian atmosphere using only the night time humidity. Remarkably even the fungal component of the lichen, which needs oxygen, survived, getting enough oxygen from the algal component. It not only survived but adapted, metabolized and got better at photosynthesis for as long as the experiment lasted. They are naturally blown over by their own experiments :). I don't think many expected that, and even if you are one of the skeptics I think you can agree that their enthusiasm for present day life on Mars is understandable.

Charles Cockell has another slant on it that is rather more skeptical of present day life at least on the surface. It all depends on how easy it is for life to get started on a planet, how easy it is to get from Earth if transferred in the early solar system, and whether it evolved far enough to spread beyond its initial habitat, e.g. hydrothermal vents, and whether it became hardy enough to survive in the hostile surface conditions there today. It could have evolved and gone extinct multiple times.

It's not necessarily the case that Mars is either habited or uninhabited. Maybe sometimes it is, other times isn't, life goes extinct and re-evolves, arose recently, went extinct long go, there are many possibilities. Charles Cockell explored this in some papers on "Trajectories of Martian Habitability" and has a special interest in the possibilities for uninhabited habitats on Mars.

Mars could also have uninhabited habitats, mixed with habited ones. E.g. some of the RSL's have life and others don't, slightly different conditions or just the life didn't get to some of them yet - perhaps it spreads slowly (we don't know how it spreads or how easily the dust can carry native Martian life around Mars). Or there's life deep underground but not on the surface.

One can think of many things that might make Martian life less able to colonize habitats than Earth life. And one interesting possiblity for instanceis that Martian life might never have developed photosynthesis. It could also be some early form of life that is not so versatile and only lives in rather favoured habitats, whatever its preferences are.

So anyway his ideas lead to many possible ways that present day Mars could be uninhabited because it is either uninhabitable, or the surface habitats just are not habited by any form of life at present, maybe long extinct or deep underground. With that background it's natural to be rather skeptical about the possibility of present day surface or near surface life. But he isn't saying it is impossible and has written many papers looking at the whole topic from many angles, indeed, he is one of the astrobiologists I most often use as sources in my blog posts because his articles are so comprehensive and thorough.

Andrew Schuerger is another researcher who often suggest it's reasonably likely the Mars surface is sterile. His special research topic is into factors on the Mars surface that impact on viability for microbes. He sees a surface with numerous conditions hostile to microbes and is skeptical about whether there is any life there. Even though none of the factors he found are totally sterilizing, he thinks the combination may make it hard for any present day life to survive there, even if there are habitats for it. Our harshest deserts do have some life. But the deserts there are even harsher than any Earth desert - will they still have life?

Meanwhile, to turn back to the optimistic side of things again, Gilbert Levin has been saying ever since his experiment flew to Mars with Viking in the 1970s that he may have detected the carbon dioxide or methane of Martian microbes exhaling gases as they ate some chemicals (amino acids) fed to them by his experiment. His experiment was confused by the same unexpected chemistry (we now know to be perchlorates) that confused all the other experiments on Viking in one way or another.

He doesn't know for sure and wants to go back to check - but his view would be a quite high percentage probability that we have found life there already and that if we were to send a new version of his experiment which feeds only one type of each amino acid and not its mirror image copy, that it is likely to confirm present day life on Mars, almost anywhere, probably as spores in the dust.

There are a few others that agree with him and a few years back it got some extra support when Joseph Miller, an expert in the day / night rhythms of life (circadian rhythms) got hold of the raw Viking data (a story in its own right, with some great detective work by its curators) and analysed them again and found that they were offset by a massive two hours from the temperature cycle. According to Joseph Miller, chemistry can only explain an offset of about twenty minutes.

We have day / night rhythms when we sleep at night and eat during the day. Well microbes do too. These are called circadian rhythms and these patterns were discovered many years later in the Viking labeled release data. The interesting thing is that they are significantly offset from the temperature variations, which to an expert on circadian rhythms who spotted this, strongly suggested that these rhythms come from  life rather than non life processes.

More on this in my online article Rhythms From Martian Sands - What Did Our Viking Landers Find in 1976? Astonishingly, We Don't Know,

This idea that Viking could have detected life already also got a boost with modern discoveries and ideas leading to the possibility that there could be habitats for life almost anywhere on Mars. And - I don't know if anyone else is making this connection, but later on I'll mention that the discovery by Curiosity of cold brines that may be too cold for life 2 cms below the surface - well it still might have Martian life in it. If so life could be rather abundant on Mars. If you are looking for a reason why Viking might have found it so easily, well, that could be one way to explain it. The Viking trenches were quite deep, could they have dug up some life from these layers of brines? Or just spores in the dust blown from a nearby brine with life in it? Levin himself has suggested that there may be layers of humidity trapped near the surface as the frosts melt in the early morning by overlying layers of cold air above the warming surface, leading to possibilities of high humidity briefly at a reasonable temperature for life. Chris McKay has agreed that this could be a possible way to improve habitability of the surface. For their idea, with Chris McKay's comments on it see Can Liquid Water Exist on Present-Day Mars?

Trenches dug by Viking 1, first trenches dug on Mars. Did it find life in the 1970s? Gilbert Levin thinks it might have and Joseph Miller, an expert in circadian rhythms, has come around to the same view and supports him in this due to some anomalies such as the 2 hours offset from temperatures. Gilbert Levin wants to send an update of his instrument to Mars which he designed soon after the confusing results from Viking in the 1970s, but with a shift of focus of NASA towards searching for habitability instead of life, we haven't sent any instruments specifically to search for life since then. So, his experiment results remain ambiguous for now with some saying that it may have found life, probably most Mars scientists pretty sure it didn't, and no way to come to a final decision until whenever we send an in situ bio detection suite of instruments to Mars with the ability to dig trenches and repeat the experiment.

For more on some of this see my

Basically you pick your favourite expert and get anything from close to 0% of surface life to close to 100% including the possibility we may have found it already in the 1970s, .

Most of them think that deep subsurface life, kilometers down, is quite likely and maybe in area of hot rock close to the surface, meters to hundreds of meters perhaps, heated by geothermal heating (there is evidence that Mars is not yet totally inactive, may even have undetected fumaroles, we'll see if TGO picks up any traces of volcanic gas emissions). So - subsurface life is a rather popular view amongst those who are not so sure about surface life. Note, even life in caves is likely to have some communications with the surface, and you can't say that because it is subsurface it can't be contaminated, as some try to say. If it is very deep down, kilometers down probably, yes. Otherwise depends on the conditions and cave systems.

Anyway - when it comes to the surface, it's mainly to do with how habitable they think the salty brines are likely to be which is mainly speculation as we haven't looked at them close up. It also depends on how impressed they are or not by the numerous other suggestions for habitats - e.g. fresh water forming under clear ice in polar regions, high humidity in salt micropores at low altitudes. etc.

As for planetary protection discussions - nowadays mostly both sides of any argument just take it for granted as an assumption in the discussion that we will introduce Earth life to Mars irreversibly once humans land on Mars. There is a long running debate right now in Astrobiology magazine between Dirk Schulze-Makuch.and Alberto Farien, and the two former planetary protection officers Jim Rummel and Cassie Conley on whether or not we should drop current planetary protection measures and send "dirty rovers" to study Mars. In this debate both are agreed that when humans land on Mars - which they both assume is inevitable, that it will irreversibly introduce Earth life to the planet. Similarly Chris McKay used to talk about reversible exploration of Mars by humans, throwing the dust up to sterilize it in the UV radiation from the sun when they leave if necessary to keep the Mars surface sterile. But with all the new results about Mars, I understand that he now thinks in terms of irreversible contamination after a human landing, like everyone else. It could be slow irreversible contamination or fast but they assume that once you have humans land on Mars sooner or perhaps much later, Earth life will colonize the planet anywhere where it's possible for it to survive.

(I hope I have got this right. Most of this is from their papers and video talks, if I have got something wrong here do say!).

Before I get on to the details of the likely legal obligations, and why Earth needs protection, I’d like to reassure you that I am keen on humans in space.

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I am an Apollo era kid. I watched the Moon landings with great interest and excitement as a teenager, and am keen on humans in space, as explorers, and perhaps eventually settlers.

However I feel strongly that the safety of Earth is our top priority, ranking high over any attempt at a space colony. I do not think we should set up a space colony if in the process there is even a small risk of endangering the environment of Earth.

I also think that valuing science is essential and especially I can’t support any proposal to act in such a way as to risk making any native Martian life extinct before we know what it is, or even if it is there or not.

One thing that I think will relieve the immediate pressure on Mars as a destination, is that we are likely to go to the Moon first. It is the natural place to begin. Many experts, including astronauts, would say we are likely to explore the Moon for some time before we are ready to travel further afield. Yes, the private space may give us the ability to do heavy lift a little sooner than expected. But there is a lot more to interplanetary travel for humans than solving the payload issues. Indeed life support is probably the toughest issue of all to get right, with the crew months or even years away from any chance of rescue or any food, water, or breathable air other than whatever they have with them.

I don’t know of any astronauts that say we have to ignore the Moon. Even Buzz Aldrin, passionate about Mars, says “Just because I am PASSIONATE about motivating people to explore Mars doesn't mean that I think we should forget about the Moon. I know we can enjoy numerous benefits by exploring and building an outpost of some sort on the Moon."

He also talks about the need to prepare, before doing expensive things and talks about sending humans to the moons of Mars before going to Mars.

(Click to watch on YouTube)

"... And the next one is that you go to Mars and you inhabit Mars. Now you can inhabit Mars right from the get go, from the beginning. That is the more determined way, that is the more economic way, but you have to prepare ahead, ahead of doing expensive things, like sending people to the moon of Mars, that's expensive, but you need them there to make the finishing touches, and what you've done to prepare permanence from Earth."

"Now you've got to be smart to be able to do all of those and to be able to do those in an economic fashion, and in an inspiring and in an international co-operative way."

"... Let's pick the best design and co-operate in carrying out that design. And that's my guiding light for low Earth orbit and lunar activities and carrying on to Mars."

See these sections in my “Case for Moon First”.

He is a very clued up guy I think, but I don't know if Buzz Aldrin has said anything on planetary protection for Mars exploration or settlement yet. If he has do say in comments or let me know!

The Moon is not “on the way” to Mars. However, we need to do space missions closer to Earth before we consider going so far afield, and the Moon is the natural place to do them, and of great interest in its own right.

It’s relatively easy to get to, at any time of the year, any year, in a couple of days. We can Medevac injured astronauts back to Earth in a few days if necessary, and you can have lifeboat spacecraft on standby for fast return of the entire crew in case of fire, chemical release, depressurization or other emergencies, just as we do for the ISS. Then there’s easy resupply from Earth if equipment breaks down, as has happened so often to the ISS in the past.

The Moon is also more interesting than we realized at the time of Apollo, with its probably vast lunar caves, and ice, carbon dioxide and ammonia ice at the poles that may be easy to extract. It also has what must be some of the easiest places to set up a first human base off-Earth with sunlight 24/7 almost year round, at the PEL’s (Peaks of (almost) Eternal Light).

There is so much to learn and do there, our eighth continent, larger in surface area than Africa and barely touched by humans so far.

Then further afield in our solar system, there are so many other places to explore, it’s so much vaster than the Moon and Mars alone. Probably eventually we will have human explorers and perhaps settlements as far as Mercury’s poles (where there seems to be ice) and in the other direction, Jupiter’s Callisto, Saturn’s Titan and further away still, we may build habitats from the materials of asteroids and comets, right out to beyond Pluto, with large thin film mirrors to collect the sunlight, and reflect it onto the light collectors for large habitats slowly spinning for artificial gravity.

However, as we explore, and eventually settle, I think we need to take care that we do this in a way that is safe for Earth and its environment, and in a way that protects the science value of our explorations. At least until we know what effects our actions will have on the celestial bodies we visit.

As for the idea some have that we just desperately must go to Mars no matter what the risk to Earth as a "backup", then for another perspective:

I cover the prospects of our future explorations further away in the solar system in more detail in my online / kindle books and my

But here our focus is on Mars. And what I describe here is not just a particular vision for the future that I hope will inspire people. I think I have identified something that is likely to be legally required.

The natural place to start is the Outer Space Treaty, though as we’ll see, it may not be strong enough by itself.

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Most of the planetary protection to date has been done on the basis of the Outer Space Treaty. However, we have had some evidence recently that it is rather weaker for the private sector than many perhaps expected. Elon Musk was able to ignore the international guideline to file a planetary protection plan for his cherry red Tesla motor. When he launched it on an orbit as far as Mars on his maiden flight of the Falcon Heavy on February 8, 2018, he was just left to his own judgement to choose an orbit. As it turned out, it was one with no planetary protection issues.

The planetary protection guidelines are worked out in great detail, and space agencies world wide comply with them. NASA has a policy document that aligns them with these provisions, but apparently there is nothing comparable for the private sector, at least, not yet. The NASA policy document is not binding on Elon Musk or SpaceX.

He did have some communication with the planetary protection office before the launch. His plans may have been influenced by those discussions, but we have no record of whether they were or not. My concern here is not for Elon Musk particularly. It is for what the implications are for the private space sector generally. The central question is:

Which, if any, of the international planetary protection guidelines drawn up by COSPAR under the OST are currently binding on individuals?

Perhaps none of them. One space lawyer, Laura Montgomery, thinks she has found a loophole in the Outer Space Treaty for the private sector (at least, in the way the OST is implemented in the US). With her interpretations of the planetary protection clauses IX and VI of the treaty, private citizens and businesses are not explicitly required to take precautions to protect Earth or other celestial bodies.

On her interpretation, if US private citizens ignore those precautions, the only requirement on the US government is to notify other states party to it that one of its citizens is not complying with the clauses on planetary protection. She says that this is as far as its authority extends. It can’t use the OST as a basis to enforce the guidelines on its citizens.

Other space lawyers interpret the OST differently. However, she thinks that her interpretation is a valid one and that Congress may have to legislate on this matter, for US citizens. If they legislated in favour of her interpretation, it would then be up to individuals to decide for themselves whether they care enough for the science value of the search for life to take precautions to prevent forward contamination of Mars.

Perhaps she might get a surprise if this matter is brought before Congress? I think there may be at least some chance that they would legislate in favour of requiring the private sector to comply with the same guidelines as NASA. What could the purpose be for a provision to protect Earth and other celestial bodies that only binds governments and their organizations, and not their citizens?

Yes, there would be those arguing that the provisions in the OST stand in the way of being the first to repeat the success of Apollo on Mars. They would also argue that taking steps to protect Earth and Mars would delay the prospects for immediate Mars colonization. However, others would talk about how planetary protection is needed to protect what could potentially be the most important discovery in biology since the helical structure of DNA. They might well go on to talk about the benefits that could follow from the science, which could have far reaching effects in medicine, nanotechnology, new materials, agriculture, and so on.

Then, if the experts say, as they would, that in the backwards direction there is a small chance of a disease that kills thousands of people, or something that degrades Earth’s environment, as a result of waiving planetary protection for the private sector - this would seem a significant downside to all except some of the most ardent colonization advocates.

Then, though Mars has its advocates who say it can be colonized easily, there are others who are less convinced by this. It is a barren rock which gets so cold at night that dry ice often freezes out as the Martian frosts even at its “tropics”. The air is so thin, that you can’t even use the oxygen in your lungs without a full body pressurized spacesuit, because the moisture lining your lungs would boil. And it can’t be terraformed quickly. That’s a thousands of years megaproject - or not possible at all.

Of course the private sector can choose their own priorities, but if they try to argue we have to open up Mars to colonization right away, so urgently that we have to ignore safety provisions to protect Earth - that argument is likely to be undermined by the sheer inhospitality of present day Mars, and the nearness, potential commercial value, and attainability of the Moon.

All this would influence the decisions.

For more on this see my note on her suggestion here. For a more detailed summary with comments and links to her own work, see my Does planetary protection law for private individuals need to be clarified in the US?

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In short the situation is a little unclear in the forwards direction from Earth to Mars. If Laura Montgomery is correct, we can’t yet rely on the OST to provide any planetary protection for private sector missions from the US, until this matter is clarified in Congress. Also, even if it provides some protection, the precedent of Elon Musk’s Tesla Roadster suggests that the private sector may still be left largely to their own discretion to decide how exactly to implement the provisions in the OST.

At present, the role of the scientific specialists in the planetary protection office seems to be purely advisory for private missions. Future legislation could strengthen, as well as weaken their role, but we can’t count on this yet.

However, in the other direction, when it comes to protecting Earth, we have much more than the Outer Space Treaty and the planetary protection officers to protect us.

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So long as the astronauts plan to return to Earth eventually, all the legislation to protect Earth’s environment applies, as Margaret Race explored in her legal review paper for a robotic sample return (Planetary Protection, Legal Ambiguity, and the Decision Making Process for Mars Sample Return).

This legislation is new since Apollo, and extensive, with many domestic laws and international treaties to navigate. It is also backed by strong public and governmental support, because of the increasing awareness over the last half century that yes, indeed, we can harm the environment of Earth. It’s become clear through many incidents that our Earth does sometimes need protection.

This is now legislation with real teeth to it.

SpaceX, can’t ignore the requirement to file an Environmental Impact Statement for a manned mission to Mars, in the way that they ignored the international COSPAR guideline to file a planetary protection plan for their Tesla roadster. This takes several years to complete.

However that’s just a small part of what’s required in the case of a Martian sample return, which is what a manned mission to Mars would be, if any Martian dust gets into the habitat. Indeed, the private sector might already encounter these requirements before then. They plan to land habitats and fuel and oxygen generating equipment, and if SpaceX uses a reusable rocket such as the BFR they are working on at present, then the return mission would also count as a sample return, whether designed as such or not. That’s because fine Martian dust would be sure to get into and on the BFR, and so, returned to Earth.

This then becomes vast in its legal ramifications, involving the Environment Protection Agency, Occupational Health and Safety Administration, etc. It is also likely to need a presidential directive, which lasts several years and is done only after the other legislation is completed. On top of all that, there are international treaties and domestic laws of other countries.

Once you have completed the legal process, which is so complex it seems optimistic to complete it in a decade, you have to build and test the elaborate receiving facility to make sure it complies.

These laws to protect Earth’s environment are already in place. For example, Cassini couldn’t launch until its radioisotope was cleared. NASA needed formal approval from the White House Office of Science and Technology Policy (OSTP)

NASA Receives Approval to Launch Cassini Mission

That approval is required by presidential directive.

“Before Administrator Goldin sent the request for launch approval to OSTP, two separate processes were completed to address the environmental and safety aspects of the mission. NASA completed an Environmental Impact Statement in June 1995 and a supplement in June 1997, as required by the National Environmental Policy Act and NASA policy. “

The same thing applies to any mission which carries a radioisotop source. We know how to contian them safely but it still needs to go through the process of an EIS. Mars 2020 has to go through the same process. No public hysteria this time AFAIK but still had to have an EIS before they could approve the launch. Final Environmental Impact Statement for Mars 2020. This is nothing to do with it being a NASA mission. If SpaceX want to launch a radioisotope heat source to space too, they have to go through the same process.

In the case of a sample return mission that is just the start of one of numerous legal procedures they have to go through. Margaret Race explored this legislation in her legal review paper for a robotic sample return (Planetary Protection, Legal Ambiguity, and the Decision Making Process for Mars Sample Return).

My summary of her paper (sadly behind a paywall) is

She found that under the National Environmental Policy Act (NEPA) (which did not exist in the Apollo era) a formal environment impact statement is likely to be required, and public hearings during which all the issues would be aired openly. This process is likely to take up to several years to complete.

During this process, she found, the full range of worst accident scenarios, impact, and project alternatives would be played out in the public arena. Other agencies such as the Environment Protection Agency, Occupational Health and Safety Administration, etc, may also get involved in the decision making process.

The laws on quarantine will also need to be clarified as the regulations for the Apollo program were rescinded. In the Apollo era, NASA delayed announcement of its quarantine regulations until the day Apollo was launched, so bypassing the requirement for public debate - something that would be unlikely to be tolerated today.

It is also probable that the presidential directive NSC-25 will apply which requires a review of large scale alleged effects on the environment and is carried out subsequent to the other domestic reviews and through a long process, leads eventually to presidential approval of the launch.

Then apart from those domestic legal hurdles, there are numerous international regulations and treaties to be negotiated in the case of a Mars Sample Return, especially those relating to environmental protection and health. She concluded that the public of necessity has a significant role to play in the development of the policies governing Mars Sample Return

All that would be required of SpaceX if they return even a small amount of dust from Mars. They will encounter this legislation already at an early stage if they send a BFR to Mars to place assets there and it returns to Earth. And the reason that this legislation would be triggered is because experts, asked if there is a risk of it returning a microbe that would harm humans or Earth’s environment, would say “Yes”. As they have for many previous studies of a sample return.

So - to launch astronauts to Mars at the least you’d have to go through that - but a lot more. It would need approval from the White House. It is for their citizens not the launch method. Elon Musk can't get around it by launching from international waters or by launching for some other country.

These are not laws to prevent people traveling into space. Go to the Moon or an asteroid or the moons of Mars, no problem. I don’t think there would be any laws to protect Earth triggered. The Outer Space Treaty obligations are minimal. Just to document what you do, including any crash, deliberate or by mistake, so you don't confuse science study of the body, if scientists discover debris from your crash they know how it got there. It's unclear whether private space in the US would be required to do that from Elon Musk's example. I think they should be required to document what htey do myself, with minimal overhead. But right now there's nothing apparently. I think it would just be approved through the FAA in that case.

Go to Mars though - and whatever the status of the OST, you have the laws to protect Earth’s environment. Those are the ones that can't be ignored.

So the approval is for an activity that may be hazardous to the environment of Earth. It’s not approval for humans to go into space.

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We’ll look at astronauts later, and the what Carl Sagan called the “vexed question” of quarantine periods, but let’s look at a rock sample first. As you read this, try to think how you might apply the same precautions to an astronaut who enters the chain of contact with the Martian surface. Is it going to be possible?

Of course, one method for a robotic sample return would be to just put the sample into a big hollow platinum sphere sealed in such a way that it will survive all the way to the ground even in the event of a crash (spherical fuel tanks of final stage rockets survive re-entry). Land it in a remote desert, never move it, never open it up, and enclose it in tons of concrete soon after the landing. There isn’t much to go wrong. But that’s pointless.

If you move it around on some form of transport that can crash, or if you have transport that can crash into it, or into the sample return building, or if you have the potential of terrorists, it is much harder. The ESF study just raised these points without answering them, saying it is outside their remit (see Mars Sample Return backward contamination – Strategic advice and requirements). These issues would have to be considered in a legal review.

If you also have to

  • keep Earth contamination away from the sample
  • prevent Martian contamination getting out, at the tens of nanometers level (it has to protect against gene transfer agents, and also possibly minute alien life with microbes only 50 nm in diameter)
  • study it with sophisticated instruments inside the facility while still contained
  • and extract sterilized samples to share outside the facility at an early stage

- that's when it becomes a half billion dollar facility, satisfying requirements that have never before been simultaneously satisfied in the same facility before.

It also introduces the possibilities of carelessness or someone making an executive decision to ignore a precaution. If anyone does that, it then makes the whole thing into a merely symbolic exercise (as happened several times with the Apollo sample returns).

The studies predict that building and testing such a facility, and training the staff to avoid those issues, will require an additional decade or more after the requirements have been set out. (See the NRC study Assessment of Planetary Protection Requirements for Mars Sample Return Missions, page 59)

NASA guidelines require the legislation to be completed before the building of the facility starts. If we want to return an unsterilized sample of Martian rock to inside a box on Earth, by 2040, it may already be too late to begin, to complete the process by then. I go into this in more detail here:

I suggested in that article that if you want to return an unsterilized sample to the vicinity of Earth before 2040, the best choice would be to return it to above Geostationary Earth Orbit (GEO) instead. This would bypass all these legal and practical complexities. So long as it is studied telerobotically in the first instance, and any materials returned to Earth are sterilized, the whole thing could be done just as it is for comet and asteroid sample returns, under COSPAR without any need to introduce new regulations.

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While researching on this topic, I was rather astonished to find that nobody seems to be giving any thought to this yet, even for a robotic sample return.

NASA is pressing ahead with their Mars sample return mission project, Mars 2020, which is due to launch in two years time to cache samples on Mars for a later mission to return to Earth. It is their flagship project for robotic spaceflight for the current decade, and they expect the sample retrieval mission to be their flagship project for the 2030s. You can read their papers on possible designs for the next mission after Mars 2020, on the rover to collect those caches and the sample return rocket to return them. They have studied details of the payload, the heatshield, and methods to break the chain of contact with Mars.

Yet, AFAIK there is nothing at all published about the legal process or any attempt at a timeline for this and for the long process of building and commissioning the sample return facility. Perhaps they just think it would be like Apollo?

If any of you know of anything on this in the papers or discussions of a Mars sample return, do let me know in the comments!

Margaret Race’s paper about the legal requirements for a Mars sample return seems to be largely ignored so far.

They will not be able to ignore these requirements when they start to plan the sample return mission in detail.

I’d like to make it clear - I’m not a lawyer myself. When I say these things, I’m relying on Margaret Race’s analysis and her conclusions in that paper. But nobody else is considering this. It’s not as if the NASA papers said “We’ve considered Margaret Race’s analysis and it won’t apply to our proposed robotic sample return because of x y z”. It is just not mentioned. Her analysis seems thorough and convincing, and I haven’t seen any suggestion of a reason why it might not apply.

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Most of this, and perhaps more would apply to an astronaut mission to Mars. An astronaut return would certainly count as a sample return, even if they don’t take any rocks back, through spores that came into the habitat on the dust.

So let’s look at how this applies to an astronaut. I’m using this to argue here that the astronauts have to do the first astrobiological exploration of Mars from orbit.

Is that right, or could astronauts land on the surface, and do an astrobiology survey right away, consistent with the current laws to protect Earth’s environment?

Again - I don’t know of anything on this either, the application of the laws on sample returns to astronaut missions. Most articles on astronaut missions to Mars, even in the academic planetary protection discussions, talk about use of quarantine, like Apollo, as the way they would protect Earth. But they only mention it in passing, briefly, have not yet got into any details such as the quarantine period, and do not do a review of the process by which this would become law and then implemented.

As we’ll see, microbial spores would survive quarantine, leading to many issues with relying on quarantine. This is a matter that would need to be examined in detail, as they go through the legislation to protect Earth, not available at the time of Apollo.

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There might be no viable spores of Martian life in the dust of course. If not, and if there is no life at the landing site either, there would be no back contamination risk. So, let’s look at this closely.

The dust storms are the main issue here. They block out much of the UV. They have fast winds and the storms become global at times. From what we know so far, it seems that they could carry viable spores of life from anywhere on Mars.

What’s more, Curiosity found salty water (brines), a few centimeters below its tracks, whenever it crosses the dunes. This is perhaps our most certain detection of present day water on Mars to date. It detected the salty water indirectly, through measuring humidity, but they are confident in their conclusions.

Although the Martian air is very dry in the daytime, at night it gets so cold that the relative humidity goes right up. So much so that it can form frost layers, though it needs a bit of help from dry ice to get the ice out of the atmosphere:

Martian frosts photographed by Viking -the light coloured material. It’s probably only about a thousandth of an inch thick. There is little by way of water vapour in the atmosphere but at night the air becomes so cold that the relative humidity becomes high.

When it gets cold enough for dry ice to form on dust particles, these fall out of the atmosphere, along with water ice. The dry ice evaporates but the water ice can build up to this thin frost layer in the Utopia Planitia area explored by Viking 2. Catalog Page for PIA00571

Salt can take up moisture from the air in the same conditions of high relative humidity at night that can lead to the Martian frosts. Some of the Martian salts such as the perchlorates are especially good at this.

Curiosity found clear signs of these cold salty layers of water by detecting rising humidity whenever it crossed dunes on Mars. (see Transient liquid water and water activity at Gale crater on Mars.). The scientists concluded that they form a couple of centimeters below the surface of the dunes in the morning and evening.

These particular layers of salty water are either very cold, or at times warm enough for Earth life, but too salty. So they seem likely to be uninhabitable to Earth life, “as is”. However, Nilton Renno suggests they may be habitable to Earth life, if they have biofilms capable of creating a microclimate, retaining water through the cycle (see Mars liquid water: Curiosity confirms favorable conditions). Also, all bets are off for Martian life with unknown biochemistry. For instance, one suggestion by Dirk Schulze Makuch is that it could use perchlorates internally as an antifreeze (see A perchlorate strategy for extreme xerophilic life on Mars). So, in principle, until we know more, there could be Martian life almost anywhere, just centimeters below the surface of sand dunes in the equatorial regions.

It’s not impossible that we have found that life already, but don’t yet know that we did. Some still think that the Viking landers found life in the 1970s. This long running debate was re-opened after Joseph Miller noticed patterns in the evolved gases, resembling circadian rhythms offset from temperature variations by two hours. That’s a delay hard to explain by chemistry alone (see his Periodic analysis of the Viking lander Labeled Release experiment).

And no, you don’t sterilize the dust of Martian life just by kicking it into the air to expose it to UV. Some of our most UV hardy spores can survive hours of direct exposure to the Martian surface UV before they are completely sterilized, with one strain able to survive 28 hours of direct simulated Martian sunlight (see Bacterial survival in Martian conditions). Martian life could be at least as hardy.

Also, any dust is shielded from the UV for as long as it remains in a shadow. That could be the shadow of a rock, an astronaut, the rover, or long shadows cast by nearby hills in early morning or late evening. Also, microbes can get imbedded in minute cracks in the dust, where they will be shielded from UV by the iron oxides in the dust. UV resistant microbes imbedded in cracks could potentially be transported for long periods of time, even in direct sunlight.

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There is research that suggests that UV radiation could be made more harmful through indirect effects on the perchlorates in the dust. It can break them up into chlorates and chlorites, and these in turn will sterilize some species of spores. However, this again is a process that won’t happen in a shadow, or in dust covered by even thin layers of other dust. If the astronauts kick up some dust in a shadow, it may well be unaffected. Then, for sunlit dust, some spores may be much more hardy than the spores tested in their experiments.

When it comes to dust storms that pick up dust, most of the UV is shielded out by the dust storm itself. Only 1% of the normal direct sunlight gets through at the height of a storm. Less UV radiation means less chance of harm from chlorates and chlorites.

The upshot is that until we know more, we need to assume that there are viable spores of Martian life in the dust, and that they may even be quite common.

Those chlorates and chlorites incidentally would have much more serious and immediate effects on humans "such as respiratory difficulties, headaches, skin burns, loss of consciousness and vomiting" (quote from page 3 of this paper). This could make the airborne dust more hazardous than expected. The perchlorates already can cause problems to thyroid glands, but these additional issues are more immediate in their effect. Better keep them out of any habitats.

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Our astronauts can minimize their exposure to this dust by using the suit port, a design meant to reduce the amount of dust that gets into the habitat on either the Moon or Mars.

You crawl in through a hatch in the back of the spacesuit which remains attached to the outside of the habitat until the suit is disconnected

You enter / exit a suit port through the back of the spacesuit like this. The airlock consists of two plates that trap a cubic foot or so of air in between the back of the spacesuit and the interior of the habitat or rover. Figure from this NASA presentation.

The two plates lock together when the suit is docked and are removed as a unit, leaving any Martian air trapped in that cubic foot of space between them until the next EVA.

(Sorry in previous version of this article I'd misunderstood, thanks to Mikkel Haaheim for putting me right on this).

It’s a great idea for reducing the amount of dust that gets into the habitat, and limiting the effects of hazardous chemicals on astronauts. It should work well for that on both the Moon and Mars.

However, how could you keep out Martian surface materials, after an astronaut nicks a hole in their glove or their suit? Even a minor accident would bring the astronaut into contact with surface materials and such incidents have happened several times in EVA’s in LEO. Minor accidents - the equivalent of scrapes and grazes, stumbles and such like, are likely to be more common on a planetary surface than in zero g floating outside the ISS. More on this later.

Also, what happens if you need to repair the EVA suit?

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So anyway, that was my new thought. When you try to apply the same sample return provisions to a human who is part of the chain of contact with the Martian surface, yes as for the robotic return, they would have to complete all the legal processes and the preparations for the return mission - and not only before the return. They have to have the precautions worked out to protect Earth before they launch. It doesn’t matter how long they plan to stay, so long as they do plan to return at some stage.

So, they probably can’t land on Mars before 2040, for the same reason as for a robotic sample return.

Also, there is no way that these requirements could just be ignored. We are no longer in the Apollo era, when they could publish the planetary protection plans on the day of launch, and so avoid peer review. Nobody can pass a waver and say that we can ignore effects on Earth’s environment and human health for these missions.

But how could it work even in 2040? Remember that the mission impact statement and all those legal procedures have to include explanations of how Earth will be protected when the astronaut returns at the end of the mission.

Also, the receiving facility for them has to be built, commissioned, staff trained, and ready before they leave for Mars.

It is reasonably straightforward to keep a sample in a box indefinitely if needed. There is much more involved in keeping an astronaut in a box or protective bubble indefinitely once they are returned to Earth, if that is what is required.

But do they have to stay in it potentially indefinitely? What about the Apollo quarantines?

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You might think the answer is obvious, to use a quarantine facility as for Apollo. Quarantine them for 21 days on return to Earth. After that, they are free to leave the facility so long as they didn’t get sick while in quarantine.

However, not many know this, the Apollo regulations were informal, published on the day of launch, by NASA who never had legal authority to issue quarantine regulations, unlike, say, the CDC. The guidelines they issued never had peer review by anyone outside NASA and are nowadays considered completely inadequate. I am relying on Margaret Race's paper for these details.

So what’s wrong with a 21 day quarantine period? Well, quarantine can only protect against pathogens of humans with a known latency period. For instance the rabies quarantine period in the UK is four months, much longer than the 21 days used for Apollo 11. Leprosy can manifest as long as 20 years after first exposure.

Carl Sagan first raised this concern:

There is also the vexing question of the latency period. If we expose terrestrial organisms to Martian pathogens, how long must we wait before we can be convinced that the pathogen-host relationship is understood? For example, the latency period for leprosy is more than a decade.

The Cosmic Connection - an Extraterrestrial Perspective (1973)

The WHO Leprosy Fact Sheet gives its incubation period from first infection to onset of symptoms, as up to 20 years.

In the European Space Foundation report, incubation period is listed as the first of the list of unknowns that make it impossible to use standard models for the effects of a release and its consequences European Science Foundation - Mars Sample Return backward contamination - strategic advice - (see 5.3 Direct consequences for human health) -

Also, an Apollo style quarantine only protects against pathogens of humans. It can do nothing about, say, a spore that when released into the wild can spread over the Great Lakes as a toxic algae bloom that kills cows and dogs, or that directly attacks or competes with the plankton in the sea, the basis of the marine food chain.

A spore like that could still be viable after a quarantine of thousands of years. Astronauts don’t live long enough to survive a quarantine period that would be sufficient to prevent viable spores from contacting Earth’s environment.

For more on this see Quarantine as for Apollo won’t work (below)

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My suggestion is that we have to bypass all this with astronauts in orbit around Mars tele-operating rovers on the surface. But are there any other options to consider?

  • Could we plan to keep astronauts in a protective bubble for ever, like a patient with immune deficiency, from when they return from Mars until whenever we manage to prove that Martian life is safe for Earth?

This would have to be the plan before they leave Earth, irrespective of whether they have any symptoms, because of the need to protect Earth against any spores that may find their way onto their bodies.

What if we later find that some spores of Martian life are hazardous to our environment? They might have to stay in there for the rest of their lives. This can’t be ruled out before we do an astrobiological survey of Mars, and that’s why I said it has to be a viable plan to keep them there “for ever, to the end of their lives”.

We also have to ensure that no breach of the quarantine can happen. 

What if the spaceship with the returning astronaut crashes. It's a tragedy for the astronaut but we also need to keep the larger picture in view too. We have to return the astronaut in a spaceship that can't break apart during re-entry - or else that becomes another possible point of failure of containment.

What if the astronaut becomes seriously sick? Are they refused hospital treatment outside their bubble because of a probably small chance that this leads to degradation of the environment of Earth?

Surely such questions would be asked during any legal review of the proposed method to protect Earth, and they would need answers. If the quarantine requirement is going to be waived in the case of a need for hospital treatment, this makes it no longer an effective way to protect Earth’s environment. It becomes largely symbolic.

And what about human rights. What is the legal basis for keeping an astronaut in a quarantine indefinitely, when it is not known yet if they have anything on them that could harm Earth’s environment? Even if they agree to this before the launch, can they be held to that agreement if they change their mind and decide just to exit the facility? Especially if they become ill, and want to be let out of the facility for treatment. Or just bored. But if it is voluntary - then it is not a sure way to protect Earth. There would be many discussions here I’m sure.

If you can sort out those issues, this is a viable answer, it would protect Earth, indeed, if you kept the astronaut in orbit around Earth on return, especially far away, above GEO, it just about eliminates risks to Earth, as for the idea to return a robotic sample above GEO. But it’s not much different from the “to Mars and die” approach of “Mars One” and I think it’s unlikely to be popular. I am also not sure of the legal status if an astronaut changes their mind. I won’t take this any further.

  • Could we break contact at the Martian end of the chain of contact. Deal with the entire surface of Mars as if it was the result of a HazMat incident.

The spacesuits constantly leak air through the joints, as that is how spacesuits are designed, for mobility. The cloth can't flex because of the high internal pressure, so they have to have bearings and those are currently done with air flowing out of the suit through the bearing all the time as lubrication. But you have positive pressure inside, so perhaps that is enough to prevent microbes coming into the joints from Mars, so that transfer of microbes is one way only from Earth to Mars.

The key here is to have materials flowing in the direction away from the

However you would need to consider how you deal with an accident on Mars that tears the outer layers of their spacesuit, so letting Martian materials contact their clothes and their bodies.

If that happens then you are back to the need to contain the astronaut in a protective bubble or box on return to Earth. It would be a case of “Oops I’ve torn my glove, now we all have to spend the rest of our lives in a protective bubble, or until the Martian microbes are proven safe for Earth’s environment”.

This is especially so if the idea is to do the astrobiological survey with surface missions, rather than just a flag and footsteps type mission.

I go into this in more detail in: Breaking chain of contact on the Mars surface (below)

In a long complex search then surely accidents are almost inevitable, and the supplies needed for a Hazmat approach are also verging on impractical.

  • Finally, you can’t sterilize an astronaut of spores once they have got onto them, because anything that kills all the spores will kill the astronaut too. Our bodies are covered in spores from thousands of species, and there are as many microbial cells in or on the human body as human cells, and without our microbe companions we would die.

If someone wants to try to draw up a plan to solve all this, those are some of the issues that need to be addressed. For myself, I don’t see how it is possible in a surface mission, not for the complex missions NASA, SpaceX etc envision, and not unless you accept astronauts isolated from Earth’s environment for the rest of their lives.

I go into this in more detail in: Can you sterilize an astronaut of microbes? (below)

There are similar issues also for a robotic mission that just lands on Mars, drops off cargo, and returns. Although not designed as a sample return, if the Martian atmosphere contacted part of the spacecraft, then the atmosphere could transfer dust and microbes, and that part then joins the chain of contact with the Martian surface.

And if it’s a BFR that has landed on Mars, I don’t see how its interior can be contained on return to Earth. As soon as they open the door, that would complete the chain of contact between Earth’s environment and Mars.

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Yes, everything might change as we make new discoveries. With the Moon, scientists soon decided that it was sterile of any native life.

However Mars is not the Moon. Its vacuum is a near vacuum, but there is enough of it for cold salty brines to be stable at temperatures that may be habitable for life, and it can even have fresh water form under clear ice in polar regions and various other possible microhabitats. None of that is possible on the Moon.

If we want to complete the astrobiological survey as quickly as possible, for least cost, it seems we should do it telerobotically from orbit. But not only that, it’s hard to see how a surface mission can be possible under the laws to protect Earth’s environment, if

  • The mission is of any complexity - and for instance has a significant risk of minor accidents, torn or punctured spacesuit etc
  • And the astronauts are going to be able to return to normal activities on Earth at the end of the mission

At least, not until we have completed this astrobiological survey from orbit, and reached a point where scientists are reasonably confident in the effects of any native Martian life on Earth and native life from Earth on Mars.

In this way then the laws to protect Earth’s environment would seem to strengthen planetary protection in both ways, at least for human missions.

As for the Moon, everything may change quickly as we make new discoveries about Mars, but we can’t now in advance which way it will change.

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Private space surely care for Earth and for their astronauts. So, they should want to know if there are any biohazards on Mars, before they go there. At least if they take the warnings seriously, they should.

Planetary protection scientists sometimes seem to soft pedal on this, offer a mixed message. To paraphrase, and not quoting anyone in particular, they sometimes seem to say:

“We have to be careful and make sure we prevent harm to Earth’s environment when we return samples”

“- But don’t you worry - after we have had a chance to learn what is on Mars you will definitely be able to land humans there, just give us time to see what is there first and prove that it can’t harm you.”

But if they say we have to be careful and prevent harm to Earth’s environment, that means there has to be a chance that there are biohazards on Mars. Otherwise the whole thing would be a silly symbolic exercise. They should say:

“We have to be careful and make sure we prevent harm to Earth when we return samples.”

“After we have had a chance to learn what is on Mars, we will then know whether it is safe to land humans there or not, and know what precautions are needed if any”

Either that or follow Zubrin and say from the get go that there is no need to take any precautions.

I think he is actually uncovering a kind of inconsistency in some of the things they say. A tendency to “beat around the bush” a bit and not straight out say

“Mars life could be a biohazard for Earth life including astronauts”

It’s a case of calling a spade a spade. If Martian life could potentially be biohazardous, we need to know that, and plan accordingly. If it can’t be, we need to know that too.

If you go to the technical papers, it is abundantly clear that this is what they are saying is a possibility in the worst case, that it could be biohazardous. We will see this in a moment with Carl Sagan’s example of a Martian version of Legionnaires’ disease, and Joshua Lederberg’s warning of our cells’ potential naivete faced with their unfamiliar aggressins.

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If my reasoning here is correct, I think it is possible that the private sector could be brought around to this approach. It just makes sense all round to do a proper astrobiological survey first, before we make our next decisions. And the best way to do it, it would seem, would be through use of sterile tele-robotic avatars for orbital astronauts.

The private sector can do a lot to help speed up this search. Indeed if Elon Musk does succeed in building his BFR, it could make it possible to complete it rapidly at low cost, maybe even within the cost of normal spaceflight budgets.

I go into this in more detail in: Heavy lift technology can speed up the astrobiological survey (below)

I hope that we can find a situation where everyone is working together. I’m speaking as a space geek myself, someone who is keen on humans in space. I want to be able to cheer SpaceX on, rather than watch discouraged with a heavy heart.

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You may be skeptical that there is any risk involved here at all, and quite naturally so. Our science fiction heroes never have to deal with such issues, indeed they don’t seem to spend much or any time even checking to see if the air is breathable. In many of these stories, even if they land on a random asteroid, of all things, only a few hundred meters in diameter, it has a breathable atmosphere!

In many TV shows, like Doctor Who or Star Trek, they just step out onto an alien planet, and it is always perfectly suited for human life in all respects.

Of course we all know it would not be as simple as that. They are works of imagination by authors and script writers, whose main objective is usually to entertain or make social comments.

Just as they never check the atmosphere, our science fiction heroes and heroines in shows like Star Trek never check whether the biology is compatible either. That is unless it is necessary for it to be harmful for a plot point.

The heroes and heroines of Star Trek landing on a planet, by teleporting. They never need to give any thought to their microbial companions. Nor do they need to worry what microbes on the planet might do to them.

It is all script and story driven. If it makes for better stories, not only do all the planets have compatible biospheres, not only are the microbes always harmless to the extent they don’t even need to check, the food is even edible by humans everywhere in the galaxy too!

There are many animals in our own biosphere that eat food that is inedible or toxic for us. When it comes to another biosphere based on a different biochemistry, there may not be much we can share except perhaps for simple products like salt or alcohol, and even then your ET host’s tastes in condiments could easily be for something that kills you, so it is definitely advised to check that first :). For more about that in a fun article, see my

Microbes from Mars could easily be inedible, which might matter if they substitute for Earth microbes in the same environment.

Or they could emit (or contain) toxins that harm us, like the liver destroying toxins from green algae that often kill cattle, sometimes in large numbers. Cows are not a natural prey of green algae, as Chyba commented (see Planetary Protection: Two Relevant Terrestrial Examples). These also kill dogs at times and have harmed humans too. Algae emit many toxins that harm us and animals, including nerve toxins and toxins that damage the skin as well as those liver toxins. It is normal for microbes to emit chemicals (secondary metabolites). However, the reason they emit these particular toxins is not yet well understood though it may be to do with deterring other microscopic creatures. At any rate, this is an accidental side effect, and Martian life also could have similar accidental side effects on higher animals, or plants, even if it has never encountered them before.

But what about directly harming us?

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I’ve already covered this in my last article so I will just touch on a couple of examples.

A disease of biofilms on Mars, resembling Legionnaires’ disease, would see human lungs as like a big warm biofilm.

(Click to watch on YouTube)

Legionnaires’ disease. It uses the same method to invade our lungs as to invade a biofilm. If Mars has biofilms it may also have diseases of those biofilms that can invade human lungs.

Astrobiologists from Joshua Lederberg and Carl Sagan through to the present day all assure us that this sort of thing is possible. Not only that. It could even potentially be far worse. Our bodies are best able to fight off organisms they have encountered already. Martian life could be so unusual it doesn’t even remotely resemble anything any Earth lifeform has ever encountered. In the worst case it might be that we have no defences against it at all.

As the Nobel prize winning microbial geneticist Joshua Lederberg, founder of the subject of planetary protection in the late 1950s, wrote,

"If Martian microorganisms ever make it here, will they be totally mystified and defeated by terrestrial metabolism, perhaps even before they challenge immune defenses? Or will they have a field day in light of our own total naivete in dealing with their “aggressins”?

from: "Paradoxes of the Host-Parasite Relationship"

With Joshua Lederberg’s insights in mind, we can’t yet rule out the possibility of severe biohazards on the Martian surface. Potentially the benign seeming landscape could even hide a biohazard so lethal that all the astronauts die soon after exposure. That is what Joshua Lederberg implies with his quote.

For more on this see my last article, which also touches on some other possibilities.

In the forwards direction, even though perfectly adapted to the planet, Martian life could be especially vulnerable if it never evolved far. Perhaps what we find there is some early form of life, predating LUCA (Last Universal Common Ancestor of all Earth life). Perhaps it even predates predation and Darwinian evolution. Such life could go extinct before you know it is there.

(Click to watch on YouTube)

Video by New Scientist illustrating how life may have originated (one idea).

According to one influential theory by Carl Woese early living cells shared genes readily with each other, living a communal life in biofilms.

There would be competition of genes, but the cells don't yet compete, and there is no predation, instead evolving together in a process of massively parallel evolution. Though perfectly adapted to Mars, this early pre-Darwinian life might easily be extinguished by the more evolved life from Earth. Yet it would be one of the most momentous discoveries ever in biology.

For more on this in my last article:

These are worst cases.

If there is native Martian life, it could be that the two biospheres, Earth and Mars, interact in a wonderfully harmonious way, with species co-existing and even symbiotically benefiting each other in the same microhabitats.

However when we don’t know what is there, we have to look at the worst as well as the best cases, when planning effective ways to protect Earth, our astronauts and native Martian life.

You sometimes get the argument that Martian life can’t survive on Earth. That the conditions are too different. However, life on Mars may well be able to withstand warmth, as parts of the surface sometimes get warm at midday, and any hydrothermal systems below the surface would be as hot as they are on Earth. The surface is superoxygenated, so oxygen is not likely to be a problem. So the most versatile and adaptable microbes on Mars, its polyextremophiles, might be able to survive on Earth too. We can’t rely on oxygen, or the differences in temperature, to protect Earth from native Martian life.

For more on this: Argument that no Martian life can survive on Earth (below)

Another common argument is that Martian life gets to Earth all the time on meteorites. It is true that meteorites arrive here from Mars in tons per century but most of them have been traveling for millions of years through interplanetary space. Indeed the youngest ones left Mars at least 600,000 years ago and are completely sterile. The last chance of a viable microbe getting here was three ice ages ago. But since the rocks come from at least three meters below the surface of Mars, typically from impacts into the high southern uplands where the air is also very thin, it’s extremely unlikely that there was any life on them originally.

If you look at this argument more closely, it’s possible that no life ever got to Earth from Mars, and if it did, it’s most likely billions of years ago. And it could have caused mass extinctions too, as there are many mass extinctions that are poorly understood. At any rate, there may well be species of Martian life that can get into the astronaut habitats that would never get here on a meteorite, so we can’t use this argument to prove the safety of Martian life for Earth.

For more on this: Argument that both planets share meteorites so must share life too (below)

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There is no problem at all here for the Moon, Callisto, Mercury, and most Near Earth Asteroids.

Send all the humans you like to any of these places, millions if you like, and it won’t trigger any provisions to protect Earth’s environment.

What makes such a difference is if the destination has potential habitats for native life that could survive on Earth. For Mars, Europa, Enceladus and Ceres then it is far more than a symbolic rubber stamping exercise.

There is one destination of interest for human missions where there may be life, but if so, it is so different from Earth life it's not likely to be an issue. That's on Saturn’s moon Titan. It is the only moon with an atmosphere, so cold that it has oceans of ethane / methane. It probably has cryovolcanoes as well, however the liquid “lava” is likely to be a methane water mixture at a temperature of around -150 °C . Any life active at such cold temperatures must rely on faster chemical reactions than Earth life’s biochemistry uses, and so, it may well be so active it self destructs at the temperatures normal to us.

This would need to be investigated, Titan might have warmer habitable liquids, or it might have life in those cold conditions that still retains capabilities to adapt to warmer conditions. But there seems a reasonable chance that Titan has no planetary protection issues, and if so, it’s a natural place for a human base in the Saturn system, as we’ll see, and a far easier place for humans to live than Enceladus. When it comes to the Jupiter system, Callisto is a more natural place for a human base than Europa, because it’s outside the deadly radiation belt. So, both Jupiter and Saturn have good alternatives for human habitats which are not only as good as the ones with the most planetary protection issues, but actually are better.

Anyway it’s likely to be a while before we send humans to Europa, Enceladus or Titan. The clouds of Venus just possibly may be a planetary protection issue (some astrobiologists think there could be microbial life in its clouds), but Mars is the main destination with planetary protection that we could send humans to in the near future.

As we just saw, there is a chance that we prove:

  • That there is some life on Mars that is harmful to astronauts, or to the environment of Earth


  • That there is some life on Mars that would be significantly impacted by Earth life, extinguished completely in the worst case, or that Earth life would make the work of searching for life on Mars hard to impossible.

Or both.

It is the first of these two that would trigger all the provisions to protect the environment of Earth, and is our main focus here. Both of those examples are covered by the Outer Space Treaty but only degradation of Earth triggers all the additional precautions.

There is no chance of public reviews and legal processes ignoring warnings by experts on astrobiology of the possibility of degradation of the environment of Earth by a returned sample.

Also, you can guarantee that the experts when asked to give expert testimony for these proceedings will say that they can’t rule out the possibility of damage to Earth’s environment. I can say that with some confidence as there have been numerous Mars sample return studies. Every review, to date, has included such warnings.

This may seem “risk averse” to prospective colonists, after all it is protecting us against something that may not even exist.

After all, the examples I gave are fine enough, they would be concerns, surely everyone would agree, but they are hypothetical, have to be. We have no idea whether there is or is not life on Mars. That leads us to the precautionary principle in international law.

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The problem here is not so much that there may be risks involved, but that we are unable to quantify what those risks are. Until we can do that, then the legislators and decision makers simply don’t have the information needed to make a decision.

This is covered in the Precautionary principle

So for instance, it is common for proponents of space colonization to say

“But your concerns here are unsubstantiated, we don’t know of any life on Mars that is either harmful to Earth life or humans, or that can be harmed by Earth microbes”.

Yes of course that is true. However, that’s only because we haven’t yet had the opportunity to study any native Martian life. The Viking 1 and 2 landers are the only ones we have ever sent to Mars. Since then we have only done searches for habitability there, not life. This is something we can find the answer to in the future. For more on this:

It is just as valid to reply:

“your belief that any native Martian life plays wonderfully with Earth life with no problems at all, is totally unsubstantiated too.”

That also has to be established by searching on Mars for life to prove that it plays nicely with Earth life. Until you do that, we just don’t know.

There are different versions of the principle.

The 1998 Wingspread Statement on the Precautionary Principle puts it like this:

"When an activity raises threats of harm to human health or the environment, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically."

The 1992 Rio declaration has a weaker version of it, referring to “cost effective” measures in principle 15.

“In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall be not used as a reason for postponing cost-effective measures to prevent environmental degradation.”

In the case of Mars, we lack scientific certainty because we haven’t searched for life there since the 1970s. In that situation, searching for life with our astronauts in orbit in the first instance, rather than on the surface surely counts as a cost effective measure to prevent environmental degradation of Earth. It actually saves money over a surface mission according to the HERRO study, which is the only such study so far as far as I know.

If you argue like Zubrin that we should send humans there right away and that there is no need to take any precautions, all this is irrelevant. But if you accept the need for precautions, and the need for an astrobiological survey first - and I think that after examining the evidence and statements the legislators and general public would agree on this, then the precautionary principle says that we need to protect the Earth, at least if we can do it in a cost effective way (and the stronger version says we should do it anyway).

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If this argument is right, I hope that it will help get us all behind the natural next step, which is to do this astrobiological survey from orbit around Mars.

It is less expensive than you’d expect. Before we send humans to Mars we are likely to have much reduced cost heavy lift able to send tens of tons in one go to Mars. We already have the Falcon Heavy. In the future, we may be able to send as much as 150 tons in one go if we have Elon Musk’s BFR. What’s more, according to his optimistic projections, it may be low cost too. He is proposing that they could send 150 tons to Mars for a cost of tens of millions of dollars.

Also, even before we can send humans to Mars orbit, if we have the heavy lift, we can do a lot of exploration from Earth using fast semi-autonomous robots and high bandwidth communications. Those are two of the three things that speed up telerobotic missions from orbit.

We also have the technology of artificial real time from multi-player online gaming, based on simulating the Martian environment on Earth as you drive across it and do your experiments. All this could make a significant difference in early stages, before we have certified the environmental control systems in our spaceships as ready to take humans to Mars orbit. The main thing that would enable all this is to put broadband communication satellites into Martian orbit probably using optical laser communication back to Earth.

In this way we would have many assets already in place when the astronauts get there, and data links working and tested, and capable teams on Earth to do most of the heavy work leaving it for the astronauts in orbit to be used to their maximum for the executive capabilities. For them it might be not unlike playing a game of “civilization” stepping in from time to time to help one of the robots that is stuck on some task or needs to be operated directly for some time sensitive experiment.

With such a capability we could do a huge amount of preliminary astrobiological exploration all within normal budgets for NASA, particularly if supplemented by partners in other countries, and research teams at universities, or indeed in the private sector, with their own independent budgets that help operate the various rovers on Mars. Depending on the level of support for the survey we might have enough of an idea to make an informed decision within a decade.

Now, an informed decision doesn’t necessarily mean a “pass”.

In the very worst case, the surface of Mars could have extraterrestrial microbes that evade all Earth life’s defences, don’t notice our antibiotics, and are an extreme biohazard for Earth life.

We are used to no-go areas in our solar system for humans as a result of physical hazards. If someone wants to fly into the upper atmosphere of the sun, this is way beyond our technology, and Io and the surface of Venus are not likely to see humans any time soon.

Well, it’s not impossible that the surface of Mars is a no-go area too, even dangerous for humans. Not because of heat or ionizing radiation, but because it could be a biohazard.

We simply don’t know enough to assess it yet, or to decide how likely or unlikely this is. That’s one of the reasons why these legal measures kick in. They are there to protect us against real possibilities, not imaginary futures.

Assuming the final outcome of the decision was favourable for a landing, this need not even delay human missions to Mars. We have many life support issues to sort out first before we can send humans safely on long interplanetary flights. It may take a while before we can send them to Mars orbit.

Once we do get there, then there is much of great interest for our astronauts to do both exploring Mars from orbit and exploring its two moons. The search for life, exploring Mars by tele-robotics, will be an exciting mission for them, and for space geeks following from Earth. It will also give us the experience to make future missions to the surface much safer, if they do get the green light at the end of the astrobiology survey.

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All I’m saying is that we need to find out what is there on Mars before we make the decision about whether to introduce Earth life to Mars or return unsterilized samples from Mars to Earth. We need to know not just the upsides but the downsides as well. Then once we know that, the decision is a political one, not a scientific one. Sometimes the decision would be near unanimous, and sometimes it might be less so.

  • If we risk extinguishing Martian life - do we go ahead? Does it make a difference if we can cultivate it in the laboratory, or if we can find a way to set aside protected parks on Mars ?
  • If it’s a new disease we can protect against, but can’t say for sure that nobody will get sick or die from it, is that enough of a hazard to not send humans there?
  • If it risks a major biological impact on Earth’s environment, that could end up destroying most of the biosphere of Earth, with humans together with selected plants and animals only surviving inside enclosed habitats?
    (Probably a near unanimous “No go” decision for this one)
  • If it is harmless to humans but will cause some extinctions of other Earth life - e.g. impacts on marine food chain or agriculture or some valued habitat
  • If we will have to run our freezers at -80 °C instead of -20 °C to prevent Martian fungi from growing on our food and making it mouldy?
  • If there are no major harmful effects in either direction, no sickness or extinctions, but the mix of the two biospheres will confuse scientific study of the evolution of life on Mars
  • If there is no life - just prebiotic chemistry. In that case, there is no chance of harm in the backwards direction. However it may be one of the most common types of planet in our galaxy and its prebiotic chemistry give us insights into the origins of life. So that also can be valued and may need some protection.
  • If Earth life could change the planet in undesirable ways (can apply even if Mars is currently lifeless).

    Cassie Conley has the example of certain microbes that convert water to cement - in conditions not unlike those on Mars, anaerobic and methane rich.

    Introducing the wrong microbes in the wrong order could turn all your water supplies to cement!

    For details see: Ways our microbes could cause harm even on a lifeless Mars (below)

These are all things you’d want to know about before you make the decision, rather than after.

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None of this is prescribing anything about what we do, when we know if there is life on Mars or prebiotic chemistry or whatever is there, and know what hazards there are if any. All that is gathering information we can use to inform our decisions.

Once we know what the issues are , if any - and there may be no issues at all - we can then make our decisions. At this point it is politics inspired by science. Our decisions can be nuanced too. Some possible future decisions are to:

  • Protect certain regions of Mars if a way can be devised to do so, especially for small habitats that perhaps can be enclosed in some way
  • Find ways to cultivate native life in the laboratory, and make it a requirement that we learn to do this before we risk extinguishing it on Mars.
  • Give scientists a time period to study Mars in its present state
  • Keep humans away from Mars for a while, as we modify the planet using ecopoesis which may require us to introduce a succession of microbes one after another rather than all at once. The eventual outcome may well depend on which microbes we introduce to Mars first, and in what order we do it.
  • Find a way to isolate some area of Mars for Earth life and human use, while preserving the science value of the rest for native life or pre-biotic chemistry.

    One place suggested where humans might be somewhat isolated is the volcanic crater on the summit of Olympus Mons. It’s very high, but has challenges. Is even that crater a sufficient barrier to contain Earth microbes? And what if an attempt at landing there leads to a crash on the outer slopes of the mountain? It is also the hardest place to land, with very little aerobraking.

    However, once we understand Martian conditions better, maybe the dust storms do not spread life as readily as expected, and perhaps much of its surface is uninhabitable to Earth life. If so, it might be practical to confine Earth life to many particular areas of Mars.
  • Land humans right away and decide no protection measures are needed at all, treat it like the Moon.
  • Make it off limit for humans indefinitely, either because Martian life turns out to be too hazardous for us, or because the native life is of extraordinary interest and we don’t want to extinguish it.

All of this would help inform our decisions.

There are bound to be many views on what to do next, but at least we would make the decision based on knowing what is there.

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We can still exploit Mars with any of these options, even if we have to make it off-limits for humans altogether, or in the near future. Whether we do this is a separate question. We can mine it from orbit with telerobotics. If the surface is biohazardous, we can still export materials from Mars, if we sterilize them carefully first.

If we find native life not related to Earth life at all - that native life itself might turn out to be the most valuable thing we can “mine” from Mars. It would be like when companies search through the tropical rainforests for new drugs in species of plant never studied before. There is no knowing what might be hidden in the diversity of microbial species on Mars, especially if it has a biochemistry different from that of Earth.

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So, that’s the main argument here. Now let’s look at this in more detail, and some of the implications of it.

This is a follow on from my previous articles:

If you’ve read those articles, you may want to skip the next few sections as they go through some of the material more quickly. You may want to skip ahead to:

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In my last article, I likened potential ET microbes on other planets to unopened treasure boxes. If you were given a wooden box as an inheritance, you would surely look inside it first before deciding to put it on a bonfire to use as fuel. Maybe you don’t need the box, but you may need what is inside it.

In the same way we need to look “inside the box” of extra terrestrial microbes before we introduce Earth life irreversibly to its habitat. We could lose a biological treasure beyond compare.

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I'll look at three possibilities - RNA world cells, Woese's pre-LUCA non Darwinian life, and life based on DNA closely related to Earth microbes.

So, the first likely possibility is that we might find RNA world cells. Martian life may not have evolved as far as Earth life, and some think the tiny structures in one of our Martian meteorites ALH84001 are fossil RNA world cells, being too small for DNA based life. Opinion is divided on whether it is life or not. Well, if it is, and the RNA world cells are still there - after all, they have not survived on Earth, which may have had early RNA world cells too, but if so it is all gone. If they do survive introduction of Earth based DNA to Mars, how much easier it is to identify a cell as an RNA world cell if you have an experiment with lots of cells and only RNA, no DNA. How much harder if it is mixed up with Earth life and you can't cultivate the RNA world cells in a separate culture (nearly all Earth microbes can't be cultured yet).

However we could also lose this treasure rapidly in the worst case. We don’t know how rapidly evolution has proceeded on Mars. If it is still at such an early stage it could be even earlier than the RNA cells. It could be perfectly adapted to its environment, and yet, if it is like our vulnerable pre-LUCA life, biofilms with all capabilities shared with all the other cells in the film, through naked RNA, with no Darwinian competition and before the evolution of predation, just a few Earth microbes introduced into the biofilm, and the native life may be gone in an exponential population explosion of Earth life through the planet, carried in the sometimes global surface winds.

The introduced life may reproduce slowly, but even slowly reproducing life can spread surprisingly fast in optimal conditions. Suppose it spreads through biofilms beneath the equatorial sand-dunes. These brines should be either too cold or too salty for Earth life, but following Nilton Renno’s suggestion, perhaps native Martian biofilms transform them into microhabitats there that Earth life can inhabit. In that case, exponential growth might be quite rapid, with spores spread during the occasional Martian dust storms when they stir up the surface layers of the dust.

Carl Sagan once used an example of a microbe doubling in its population once a month for a decade, to illustrate how rapidly Earth contamination could spread to Mars. That’s a slow pace of growth similar to that for cold loving microbes. With that example, starting with a single microbe, and if not limited by surface conditions (as of course it would be), then after a decade, you end up with around a quintillion microbes per square centimeter of the surface over the entire surface of Mars (2^120/(144.1 million*10^6*10^4) )

If what we have there is like our vulnerable pre-LUCA life, perfectly adapted lateral transfer / Lamarckian biofilms with no Darwinian competition and before the evolution of predation - then the biofilms might be like a petri dish for a microbe that finds conditions there optimal for it. Just a few Earth microbes introduced into the biofilm, and the native life may soon be gone in an exponential population explosion of Earth life through the planet, carried in the sometimes global surface winds. Even the two hemispheres are not at all isolated from each other as dust storms often start in one hemisphere and then cross to the other one before expanding to a global storm.

Of course it would happen more in fits and starts. The life would spread rapidly in a small microhabitat for a few months or years, then the spores would spread to several nearby habitats in a dust storm, then spread again within those microhabitats, in a more jumpy fashion. Still, if it is spore forming and easily spread in the dust, and if there were biofilms it could colonize throughout the equatorial regions in the sand dunes, worst case, then it might not be that long before you have patches of Earth life throughout the surface of Mars. In this worst case, it might not take that many decades to make native life in the easily accessible surface habitats everywhere extinct.

Then, if Martian life is based on DNA, it's still potentially confusing to introduce Earth life. For as long as there is only native life there, you just need a single strand of DNA, or a single spore that we can extract a sequence from and we identify it as DNA based life. If we introduce Earth life then we will find DNA everywhere. How do we know if any of it is native to Mars? We have to try sequencing it all to find non native life amongst the Earth based DNA. But we discover new phyla all the time when we sequence Earth microbes. Every DNA survey of spacecraft assembly clean rooms turns up numerous new species as just DNA sequences we know no more about. Even if we find a complete new phylum on Mars, it could easily be a new phylum from Earth that happens to find Mars conditions to its liking. We could announce it as a discovery of native life, then a decade later, find it back on Earth and have to retract that discovery. So far we have sequenced only 0.00001% of the estimated trillion species of microbes. More on that in the last article under Zubrin’s use of anthrax - this does not show that it is easy to tell native life apart

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In the other direction, from Mars to Earth, it could be anything from microbes that attack plankton in our oceans, fungi that have anti-freeze fluids inside that let them make food mouldy down to -80 °C so requiring us to run our freezers below that temperature, a disease like Legionnaires’ disease but with no cure, through to a lifeform that no higher Earth life has any defences against, or can evolve resistance to fast enough, so that it ends up eating through all except the smallest and most rapidly evolving multicellular creatures.

Pathogens do not need to adapt to megafauna to be lethal. It's rather the opposite. Pathogens are at their most lethal when they leap to a new host as it is in their interest to keep their host alive.

I gave the quote from he Nobel prize winning microbial geneticist Joshua Lederberg, founder of the subject of planetary protection in the 1950s, here it is again

Joshua Lederberg: "If Martian microorganisms ever make it here, will they be totally mystified and defeated by terrestrial metabolism, perhaps even before they challenge immune defenses? Or will they have a field day in light of our own total naivete in dealing with their “aggressins”?

from: "Paradoxes of the Host-Parasite Relationship"

(emphasis mine)

He goes into it in more detail in Parasites Face a Perpetual Dilemma:

"Whether a microorganism from Mars exists and could attack us is more conjectural. If so, it might be a zoonosis to beat all others.

"On the one hand, how could microbes from Mars be pathogenic for hosts on Earth when so many subtle adaptations are needed for any new organisms to come into a host and cause disease? On the other hand, microorganisms make little besides proteins and carbohydrates, and the human or other mammalian immune systems typically respond to peptides or carbohydrates produced by invading pathogens. Thus, although the hypothetical parasite from Mars is not adapted to live in a host from Earth, our immune systems are not equipped to cope with totally alien parasites: a conceptual impasse."

So, Joshua Lederberg is saying that our immune system and defenses are keyed to various chemicals produced by Earth life. such as peptides and carbohydrates. It's entirely possible that Mars life doesn’t use those chemicals at all.

So, in the best case (for us), the microbes are unable to make anything of terrestrial biochemistry and give up totally mystified and defeated by terrestrial metabolism”.

However, in the worst case, it’s the other way around. Microbes from Mars could just munch their way through Earth life. This time, it’s our defense systems that are mystified. The microbes don’t resemble Earth life and so our defenses wouldn't be able to recognize it as life that’s attacking us, never mind do anything about it. In this case, the microbes have a “field day in light of our own total naivete in dealing with their “aggressins”.

Here is how John Rummel put it, former NASA planetary protection officer:

John Rummel: "After living in the dirt of Mars, a pathogen could see our bodies  as a comparable host: they could treat us 'like dirt'". But to quote Donald Rumsfeld, we're dealing with unknown unknowns. It could be that even if the microbes lived inside us, they wouldn't do anything, it would just be this lump living inside you."

It is possible that a disease of Martian biofilms does not recognize our biochemistry and baffled just gives up when it encounters our lungs. On the other hand it is also possible that our lungs simply don't recognize it as a threat. As the physicist Claudius Gros put it:

"Here we presume, that general evolutionary principles hold. Namely, that biological defense mechanisms evolve only when the threat is actually present and not just a theoretical possibility. Under this assumption the outlook for two clashing complex biospheres becomes quite dire."

Developing ecospheres on transiently habitable planets: the genesis project.

In that case our lungs, never having seen anything like this Martian microbe, simply do not put up any defences at all.

Not only that, it could in the very worst case, be the situation that no higher lifeforms on Earth mount any defences against Martian life. That's a situation Gros explores for his idea to introduce new life to transiently habitable planets - but it is also relevant for life returned to Earth from elsewhere in our solar system.

If that happens the situation may be dire for the environment of Earth after life is returned to Earth from Mars. I think with our technology humans and our civilization would survive, through paraterraforming, covering Earth with vast t microbe impervious enclosures to keep the Martian life out while humans and whatever Earth species we save survive inside. Back at the time of Apollo I think such a scenario could easily have made us extinct as we didn’t have the necessary technological or biological sophistication - back then we were still using tiny metal rings wound by hand with thin wire as the memory core for the Apollo flight computer - I think many forget how primitive our technology was back then compared to what we have now.

In that worst case, and we don’t know enough to say is impossible yet, we’d survive but only in these habitats protected from the rest of Earth by barriers that the Martian microbes can't get through. Back at the time of Apollo I do not think we would have had the technology to survive such an event at all.

Perhaps this is a common fate of ET’s that return samples from nearby habitable worlds too soon in their technological development stages. Or it may be rare or never happen. We simply have no way to know.

Also, whether there are dire consequences or not, surely Earth's biosphere would be at least subtly modified. You can't substitute one microbe for another in niches throughout Earth- if Martian life can survive here - without some changes.

Surely our biosphere would be exactly the same if some of the microbial niches were inhabitant by Martian life, coexisting or competing with our microbes, with slightly different chemistry. It seems mainly a question of whether those differences would be subtle ones that only specialists notice, or major and significant ones.

They don't have to be harmful. Sometimes they might be effects we consider benign. E.g. nitrogen fixing (nitrogen is in short supply on Mars and if there is any native life capable of nitrogen fixation at such low atmospheric pressures, it is likely to be an efficient nitrogen fixer on Earth too), or a Martian microbial disease that coincidentally attacks some microbial or insect pest, or they make the soil more fertile, or they can survive in conditions Earth life can't and reverse desertification etc.

We hear a lot about the harmful effects of non native species transferred from one continent to another. What we don't hear about so often is that other non native introductions, accidental or planned, can often be beneficial. See The potential conservation value of non-native species

So, of course it could also be that Earth and the Mars biosphere get on together wonderfully. I do not mean this ironically. They could be mutually symbiotic and beneficial. If you were writing a science fiction movie and want an upbeat conclusion, you could argue for that as a plausible scenario. But unfortunately we don’t get to write the sequel in this case, and we simply don't know what to expect yet.

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There are two basic arguments given for those who say we don’t need to worry.

One of these arguments is that all microhabitats on Mars are inaccessible to humans on the surface. However that is no longer an easy case to support because

  • Mars has a far more complex geology than we used to think. It probably has extensive networks of erosional caves and some of those will be connected to the surface and may give communication with subsurface hydrothermal environments. Indeed the methane plumes, if they exist, might be evidence of such.
  • Our ideas have changed since Phoenix observed droplets of what seems likely to be salty brines form on its legs after it landed in a salt / ice region, in the dried up salt deposits that formed bed of the ancient northern ocean on Mars. It also found evidence, through isotope ratios, that the oxygen atoms in the CO2 exchanged with the surface, probably brines. Since then it’s become increasingly clear that there are brines on the surface of Mars, within the top two cms.

We now have a situation where astrobiologists now universally agree that these brines do exist. It can no longer be doubted with indirect but unambiguous humidity measurements of the presence of brines below the sand dunes as Curiosity drives over them, just a couple of centimeters below its tracks.

Those particular brines are probably uninhabitable for Earth life but potentially Martian microbes with a different biochemistry have the capability to inhabit them, which is relevant when thinking about back contamination risks. There could be Martian life and that it can live in such cold conditions does not prevent it necessarily from being also capable of living on Earth.

There are now many proposals for various ways brines can form on Mars as well as a number of features that are thought to be indirect evidence of them. The debate has turned to questions about whether particular proposed brines exist and whether some or any of them are habitable or not.

At a rough guess (based on remarks in published papers), perhaps half of all astrobiologists are skeptical that there are any near surface habitats that Earth life can inhabit, and perhaps half think it is likely that such habitats exist somewhere on Mars, possibly even pervasive over much of Mars.

Some, especially astrobiologists for DLR (German aerospace) as a result of their Mars simulation experiments think some Earth life may be able to grow on Mars using just the humidity in the atmosphere - it is very dry in the day time but approaches 100% at night. Some Earth life can manage this trick and their experiments suggest it may be possible on Mars too with some lichens and cyanobacteria showing promising results.

So this idea that the surface of Mars is uninhabitable to Earth life is not one we can take for granted any more. It may be, but again it might not be with opinion pretty much equally divided between the two possibilities.

As for Martian life, since we don’t know its capabilities, we probably have to assume that almost all the brines are at least potentially habitable by it, even if not by Earth life. This also suggests that until we know more we should assume that there are spores of life in the dust almost anywhere on Mars, from any of its many potential habitats, from the equator to the poles.

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Yes many of the brines on Mars will be very cold, well below the -20 °C limit below which Earth life replicates very slowly or not at all. But some of the brines may be warmer, depending on the chemical composition. And the deeper subsurface may have hydrothermal systems today and it definitely has had them as recently as a couple of hundred million years ago. There is also the potential for fresh water in the polar ice caps melted into layers 10–20 cm thick below a trapping layer of clear ice, a process that happens in Antarctica and should happen there too if there is clear ice, as models suggest.

Mars is also super-oxygenated, so oxygen doesn’t seem likely to be a problem. Mars may well have polyextremophiles that would have no trouble surviving on Earth. One of our top candidates for a lifeform on Earth that could survive on Mars, Chroococcidiopsis, is able to live anywhere on Earth from dry cliffs in Antarctica, through to tropical water reservoirs. At any rate we can’t rule this out.

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Now of course Zubrin argues that there is nothing to worry about because Earth and Mars share meteorites so must have life in common.

Zubrin’s meteorite argument is not accepted by experts on panspermia. It does work for comets and asteroids, samples returned from them are fine because Earth receives similar materials all the time. But sadly you can’t use the same argument for Mars.

I go into this article in detail in my previous article in these sections:

So, this is a short summary.

First, remember it is not enough to show that it is possible that some species from Mars can get to Earth in a meteorite. You have to show that any Martian species that has the potential to survive on Earth and perhaps cause problems here can get here on a meteorite.

Though it is possible for life to be transferred in both directions, we do not know if it happened. Although we receive tons a year of meteorites, they are all sterilized at present as the most recent impact on Mars to send rocks our way was 600,000 years ago. The rocks were at most 2 meters diameter, most of them only 60 cm in diameter. At 2 meters then even radiodurans, one of our most hardy microbes, would get a millionfold reduction in population in less than 67,000 years (see table 1 of this paper, ionizing radiation levels on Mars are less than half those in interplanetary space).

So if any viable life did get here, it happened three ice ages ago.

But those meteorites come from at least three meters below the surface of Mars, a cold dry planet, and most from the southern uplands where the air is thinner (so easier for rocks to get into space). It is very unlikely that any life got into any of the meteorites.

There are many other obstacles including the minimum shock of a sudden pressure of five thousand atmospheres, which many microbes from Earth can’t survive. We do not know if any Martian life can survive that. Then the transfer in the vacuum and cold of space. And fireball of entry to Earth’s atmosphere. Life may have got here from Mars as recently as 600,000 years ago, three ice ages previously. Or it could be the last time it happened was over 3 billion years ago. Or it may never have happened at all.

And there is no way to know if any Martian life has caused mass extinctions on Earth. Indeed it is not impossible that Martian life caused the Great Oxygenation Event, which radically changed Earth’s environment by introducing oxygen for the first time to its air and oceans and may have caused a mass extinction too.

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Obstacles are as great in the other direction or greater from Earth to Mars. This time the meteorite does have life on it as it leaves Earth, almost certainly. But it has to leave our atmosphere at over 11.2 km/sec and the last time that was possible was 66 million years ago. To leave at such speed it has to be a fireball on its journey all the way through the atmosphere sterilizing its surface and any cracks that lead into its interior through plasma sterilization.

Then on arrival on Mars then it finds a dry planet with few habitats and any life that remains inside the rock has to get out before it is sterilized by cosmic radiation, find a suitable habitat and must be pre-adapted to it. It is not clear that this has ever happened.

So again - it might have happened 66 million years ago. Perhaps well over 3 billion years ago if early life back then was hardy enough as there were huge 100 km diameter impactors that blew away chunks of Earth’s atmosphere so fixing the fireball problem, and Mars also had seas and lakes. But it may never have happened.

Astrobiologists certainly do not know the answer here. They feel they need to devise experiments on Mars to be able to detect any kind of alien astrobiology and do not feel they can assume that it is identical in its biochemistry to Earth life.

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This is the key insight for this article. It doesn’t seem possible, or at least practical, to break chain of contact between Mars and Earth for a human mission.

If a Mars transfer vehicle docs with the ISS first, say, it makes no difference. It just adds the ISS to the spaceships that join the chain of contact all the way back to the Mars surface.

But let’s look more closely at the three main possibilities, quarantine, sterilizing an astronaut of spores, and breaking the chain of contact at Mars.

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Quarantine works fine for protecting against a known hazard. If you want to protect against import of rabies to your country, a quarantine of four months is nowadays considered sufficient for the UK (which is rabies free). For leprosy however then it may be symptom free for 20 years after infection. So it doesn’t work so well when you have an unknown hazard. And even the rabies quarantine period is far longer than the three weeks for the Apollo astronauts.

As I said above, NASA never had legal authority to issue quarantine regulations, unlike, say, the CDC. The guidelines they issued had no peer review by anyone outside NASA. I am relying on Margaret Race's paper for these details.

Even at the time the rules they made were breached in many ways. There were several times the advisors they consulted told the mission planners to do it one way but in order to make things more comfortable for the astronauts they did it in another way that would have endangered Earth's environment if there was any life in the sample. At the time most people thought that the Moon was very unlikely to have any life, and so they treated it almost as a formality with the result that basically the regulations provided no protection at all and they almost might as well not have done them. It is more a kind of symbolic gesture that they thought it mattered.

The first time they endangered Earth's environment (if the lunar dust had been biohazardous) was during the descent, venting air from the command module. Then when they landed, they opened the hatch in the open sea because they didn't want he astronauts to become seasick waiting for a crane to hoist them onto a ship. The astronauts put on decontamination suits but dust from the module would have got into the sea as soon oas they opened the door as it was everywhere inside, in the air. The astronauts said the dust smelt like gunpowder - a bit of a mystery as nobody can quite work out why it would, as it doesn't contain ingredients that resemble gunpowder.

None of these were lapses of attention. They were executive decisions by the higher management at NASA to prioritize the comfort of the astronauts over the protection of Earth’s environment, against the advice of their planetary protection advisors. Though there were lapses of attention as well as other executive on the spot decisions to ignore regulations during the lunar sample cu rating.

They didn’t actually have enough understanding of biology back then to protect Earth’s environment, as we now know. We were lucky, there was no life on the Moon. But we don’t have any assurance that the situation is the same for Mars, and those provisions are regarded as most instructive for what they tell us about what can go wrong. Meltzer’s “When Biospheres Collide” goes into this in great detail.

Then, it was never clear, as far as I can tell, what they would have done if any of the astronauts got ill in quarantine.

You don't learn much from quarantining astronauts except to endanger their lives. If they fall sick, what do you do next? You don't know if it was Martian microbes or Earth microbes that did it.

Suppose you quarantine in a space station above Earth, for an extra year say. If they get sick, do you just leave them in orbit to die when they could probably have their lives saved with a quick return to Earth for what may just be a normal medical emergency? It may be that you endanger their lives and there was no need for it at all.

Even if you strongly suspect it is some Martian microbe, what do you do next?

And none of this is any use if they carry spores on their bodies, harmless to humans, that could be returned to Earth and impact on its environment. Especially if Martian microbes have taken part in their personal microbiomes so that their bodies have become incubators for Martian microbes, perhaps without even knowing it if the life is hard to detect amongst Earth microbes.

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You might think, surely (as long as they are not sick of some Martian disease in their lungs or bodies), the astronauts just need to get very clean. Wash away all the spores somehow. That might work if you knew what it is you need to protect against. Surgeons are able to get clean enough for an operation but their aim is just to reduce the number of microbes, not eliminate them altogether. But for planetary protection, the requirements are far more stringent.

First, you might think you have to return large amounts of microbes to be harmful. But no one spore is enough. They use Colony-forming units to assess how sterile a spacecraft surface is, dilute the sample and spread it over a culture dish and count the colony forming units. Some of those colonies could be from a clump of several spores, others will be from a single spore. This only counts cultivable cells.

For example, although normally it takes thousands of spores to infect someone with anthrax, In one known case the victims were infected by an average of 9 spores per person and in an unlikely but not impossible scenario, even a single spore in someone's lungs might germinate and cause infection and death. See Biological Weapons

To see how hard it is to try to remove all the spores from your skin, the Viking landers were first sterilized as much as they could, without heating it. Then they put it through 30 hours of dry heat sterilization of the Viking landers at 112 °C.

Even after that, they think there were still up to 30 spores on the entire spacecraft on launch and there could have been a hundred times that number of non cultivable spores and dormant states of microbes, so about 3000.

Though those figures are considered good enough in the forwards direction, it would not be enough for a sample returned to Earth. In that direction it is thought that even a single spore is not acceptable. (The Earth is far more habitable than Mars).

Heat sterilization at 300 °C will definitely do it because no amino acids can survive at that temperature, indeed, somewhat below that is still high enough to destroy all Earth life’s amino acids. This could be used in principle to sterilize rovers because we have hardware used for extreme heat situations that can withstand such temperatures.

But that’s no good for humans, as we wouldn’t survive such heat treatment either, of course. Nor can we remove them by washing ourselves or physically removing them. That can remove many, but not all the spores.

There is no way that spore populations on humans can even begin to approach those figures of the sterilized Viking landers. Typically humans have as many microbial as human cells in their bodies. Sterilize us of non human cells and we would not function any more, if it were possible at all. Short of some incredible future nanotechnology, engineered artificial microbes or something, this is not practical.

They require that you break the chain of contact with anything that could have touched the Mars surface.

"The mission and the spacecraft design must provide a method to “ break the chain of contact” with Mars. No uncontained hardware that contacted Mars, directly or indirectly, shall be returned to Earth. Isolation of such hardware from the Mars environment shall be provided during sample container loading into the containment system, launch from Mars, and any inflight transfer operations required by the mission

from: Planetary Protection Policy

The “directly or indirectly” it counts as “uncontained hardware” if it contacted something that contacted something that ... that … that contacted the Mars surface.

Here the astronauts of course are part of the chain of contact as they have at the minimum touched something that touched the Martian surface but have probably touched it directly, the dust at least. So anything that touches one of the astronauts itself becomes part of the chain of contact and has to be isolated from Earth. That’s why if the astronauts return to the ISS, the whole ISS then has to be isolated from Earth.

It is so stringent because when you don’t know what is in the sample, you have to be able to contain. It is not just Earth life but any microbe of any conceivable biochemistry. Which could be present as hardy spores in the dust.

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Now, if you know what it is you are protecting Earth from, then you may be able to devise some method to protect Earth, to clean the astronauts of the Martian life, or a quarantine period, depending on what it is.

But if nothing happens in the habitats on Mars, or returning spaceships, it proves nothing. The spores carried by the humans on their skin, or in the air, on surfaces etc might be hazardous only to plankton in the oceans, or earthworms, or make freezer food mouldy, or they might harm cows, or dogs, or grass or any organism in Earth's environment, or change the chemistry of habitats. You can’t test everything in orbit.

Indeed, it may not be dangerous right away either. It may need to swap genes with an Earth microbe first before it can harm us. Or it might need to unlock a gene through changes in gene expression from some environmental factor not present in the ISS or it may need to do a random mutation first.

There is no way that any kind of a quarantine facility can achieve this. After all at the end of it, the astronauts simply walk out and can’t be sterilized. And they can’t test all possible interactions with Earth’s environment inside the quarantine facility.

In short, quarantine simply does not work. This was never tested at the time of Apollo because the provisions never had to pass peer review. They were largely symbolic, as it turned out.

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So if the astronaut is part of the chain of contact with Mars (something touches something touches something … touches the astronaut) then they have to be contained on returning to Earth, until proven not to have any spores on them that could be a hazard to Earth’s environment.

You could try to prevent the astronauts ever contacting the Mars surface directly or indirectly throughout the time they spend on the Martian surface perhaps. Is it a case of landing what is, essentially, an inside out Biohazard level 4 laboratory on Mars?

If you do this, you have to treat it as if what is there is unknown and deadly, either to your astronauts or to Earth itself.

Carl Sagan once said about ideas to protect a sample returned to Earth - they wanted to test it - he said they should use anthrax spores inside if they want to be sure that it is safe to return a sample from Mars.

Actually it is worse than that. We don’t have anything biological that is deadly enough to correspond to Joshua Lederberg’s worst case example.

Actually it is more strict in its requirements than a normal biohazard level 4 laboratory too. Each sample return report has been more stringent than the last. The previous one by the NRC said 200 nm was okay just after discovery of the ultramicrobacteria. Back in 1999 they were saying you can return a sample to a simple glove box in a Biohazard 4 laboratory. If anything the requirements are going to be more stringent than this.

The most recent sample return study by the European Space Foundation (ESF) based its recommendations on research that suggests that cells based on an alien biochemistry could be as small as 50 nm in diameter, a quarter of the diameter of the smallest cell to contain all the machinery of Earth life.

They also referred to other research, published just before the study, about how rapidly archaea (ancient microbes) can swap capabilities by lateral gene transfer. This is an ancient mechanism that works even between microbes more distantly related than fungi are from aphids, using Gene Transfer Agents. It is so ancient, it may also be able to transfer genes from life that had last common ancestor with us in the early solar system. In one experiment 47% of the microbes (in many phyla) in a sample of sea water left overnight with a GTA conferring antibiotic resistance had taken it up by the next day.

They concluded that if possible, the facilities should be designed so that probability should be less than one in a million that a single unsterilised particle of 0.01 µm (10 nm) diameter or greater, if possible, to contain GTA’s, and if that's not possible, that

The release of a single unsterilised particle larger than 0.05 µm [50 nm] is not acceptable under any circumstance
(See section “life as we know it and size limits” in their report)

This is because we have no idea what needs to be kept out. You have to keep out any conceivable biochemistry, cells possibly as small as 50 nm in diameter and GTAs that could be as small as 10s of nm's in diameter. It might be that the protocols used by, say, the CDC, for extreme deadly unknown hazards would work for these too, but you would have to prove that they work.

It doesn’t mean that we think there is something deadly on Mars. We simply don’t know. And in absence of knowledge, and with not just our biology but potentially any form of biochemistry out there, the only safe thing is to treat it as if it were a biologically extremely hazardous environment.

So can we keep Martian life out of the habitat to these demanding standards?


This idea comes from Mikkel Haaheim who had been certified, and regularly recertified in mass HazMat response as part of his former employment, and commented about this on my Quora draft of this post. His suggestion is inspired by the approach used by the CDC to respond to Hazardous Materials (HazMat) incidents. Although they use sterilizing agents as well, they rely mainly on a physical flow or air and water to remove contamination. If this could be adapted to a space mission, astronauts would need to do this every time they return from an EVA on the surface.

This might not be needed if the suitport can be made 100% effective. As they dock back with the habitat, a cubic foot of Martian air gets trapped in the suit lock itself between the two plates, in the spacesuit and the habitat. However these plates lock together when the spacesuit docks, and they are removed as a single unit trapping the Martian air inside.

Can the suit part be made 100% effective so that no dust enters even around the edges? And what about maintenance of the suit port and the lock mechanism?

If the suit port method can be made totally reliable so that no Mars dust ever gets inside the suit or escapes from the locked hatches, then the rest of this section might not be necessary. In that case, mark this as solved and move on to the next section, the far more tricky question: What about an accident on the surface

But if there is some way for dust to get into the spacesuit or out of the suit port lock, then we might need a process like this.

For this approach you need multiple layers of disposable outer layers, which can be sterilized or recycled, e.g. plastics melted and rewoven, or the layers are sterilized with caustic chemicals. You need equipment to blow sterilized winds constantly outwards, so the astronaut enters against a strong wind. You also need to be able to supply water rapidly in bulk as showers of uncontaminated water, to wash away contamination.

When the astronauts enter the habitat - perhaps from inside the spacesuit through the suit port, their outer layer of clothing is washed with flows of water against a constant strong wind. They then remove this layer which is later sterilized or destroyed. They then move to a different station within the airlock for a second shower and strong wind, then remove another layer. There are extra steps for someone who doesn't follow protocol, or touches the wrong thing by accident. Details in another comment here

This has the advantage that it works as a physical barrier. The idea is that even the tiniest particles are blown or washed away, so long as they are not physically bonded to the surface.

The process has to sterilizer or remove all the air in the airlock in some way.

I've been trying to find scholarly material on the CDC approach to such incidents, and how they calculate that the procedures are safe, whether it is based on probabilities or is a certainty. But so far not turned up anything. Do any of you reading this have a good source? Do say in the comments below, or join our discussion on Quora.

They would need to consider turbulence, mixing of air and brownian motion, and boundary layers of air close to a surface. The boundary layer in water is typically a tenth of a millimeter thick, velocities range down to zero at the surface, thicker in the wake of a body.

It's not just any dirt and other materials on their clothes, but submicron dust in the air as well.

If 100% certainty can achieved in this way, it would require supplies of air and water (or other liquid), perhaps stored in tanks and then sterilized of any Martian life that got into them, and cycled round again for the next EVA, and the garments resterilized or recycled etc. A HEPA filter would not be enough, the air would need to be either sterilized or filtered down to 10 nm.

I don't know how practical such an approach could be.

Then we have the issue of any samples the astronauts wish to bring into the habitat - the Mars sample return facilities started off with a simple glove box but with new discoveries in biology and results about extremophiles and theoretical ideas about possible alien cells, they became more and more complex. It’s now a $500 million facility that operated on Earth requires them to have it commissioned and in use for several years to make sure there are no breaches in the chain of contact. So - could they be as confident as that when returning a sample into the habitat? To break the chain of contact on Mars they would need the same level of assurance as to break it on Earth.

This might work for a short mission. Perhaps more Apollo 11 than Apollo 17? It's a stretch even then I think. But perhaps it is more for anyone who thinks they can make this work to formulate a more detailed explanation of how it would work.

But none of this can protect against contamination in the case of even a minor accident on the surface breaching the spacesuit.

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Whatever procedure you use, what if there is some accident on the surface, with an injured astronaut- contaminated by the Martian surface materials through a tear in the suit. Are they then just left to die on the surface? Or they are allowed back into the habitat, but then none of the astronauts can ever return to normal life on Earth again unless they prove that there are no harmful spores on Mars?

In a long months long mission some kind of incident with an astronaut minor injury seems likely enough, cuts and scrapes, or just tears of the gloves or clothes. Here are some example EVA’s in the past that lead to tears of the spacesuit which may give an idea of what could go wrong:

On June 5, 1966, Gene Cernan struggling against stiff spacesuit rips off outer layers of the suit, torn layers let the Sun through, causing hotspots on his back.

On August 15, 1979, Valeri Ryumin had to cut through four 1mm steel cables to free an antenna dish, which flopped around - leaving a small puncture in his suit’s primary bladder.

On August 15, 2007, Richard Mastracchio noticed a hole in his left glove. The EVA was terminated early though they found only one layer of five was punctured.

When EVAs Go Wrong

To this we can add another incident in 1991, which wasn’t noticed until the astronaut returned, and technicians noticed blood on the outside of the suit, and realized that the astronaut must have bled into space:

"Incidentally, we have had one experience with a suit puncture on the Shuttle flights. On STS-37, during one of my flight experiments, the palm restraint in one of the astronaut's gloves came loose and migrated until it punched a hole in the pressure bladder between his thumb and forefinger. It was not explosive decompression, just a little 1/8 inch hole, but it was exciting down here in the swamp because it was the first injury we've ever had from a suit incident. Amazingly, the astronaut in question didn't even know the puncture had occurred; he was so hopped on adrenalin it wasn't until after he got back in that he even noticed there was a painful red mark on his hand. He figured his glove was chafing and didn't worry about it. .... What happened: when the metal bar punctured the glove, the skin of the astronaut's hand partially sealed the opening. He bled into space, and at the same time his coagulating blood sealed the opening enough that the bar was retained inside the hole." Explosive Decompression

After a minor incident like that, some rough edge on a rock or the spacecraft itself, maybe sharp edge due to micrometeorite damage, or you are cutting something and it snaps back, you have a tumble and scrape your suit on a sharp rock, anything like that, and you look down and see

“Oops I’ve got a tiny puncture in my glove, now I am going to have to spend the rest of my life in a protective bubble when I get back to Earth, or stay in space for the rest of my life, or until (if) Mars life is proven safe for Earth”.

You could land an astronaut in a hamsterball perhaps, and sterilize the outside of it on return to orbit. That might work so long as they don’t tear it or exit it at any time on the surface, and have all their provisions inside.

But it’s hard to see any practical and reasonably reliable way of breaking contact at the Martian surface. Not with present day technology. At least, if you want something more than just to say you landed them there, do hardly anything on the surface, and return to orbit again.

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An Apollo 11 type flag and footprints, single EVA, maybe that’s possible, without the sample returns they did, and with many measures taken to make sure they are completely sterilized of any Martian life on return. Perhaps you could do that, following the CDC approach, and treating the surface equivalently to an extreme biohazard. The astronauts would know that they risk having to be kept above GEO or in a protective bubble for the rest of their lives if they have an accident on the surface or contact surface materials through some mistake in procedures. If it is only a short duration mission, the chances of that may be low.

If you think that is possible, and desirable, do comment and discuss it further.

But I don’t think this is what they would have in mind. Could it work for a year long mission on the Martian surface with many EVA's.

Also, it still doesn’t protect Mars in the forwards direction. The honour of being the first humans to land on Mars might swiftly change to dishonour when you realize you have been the ones to introduce Earth life to Mars for the first time.

If you had the idea of doing it just for the prestige of being first to land on Mars, the prospect of future headlines like this might give you pause for thought:

(Photograph is Hubble's photograph of a Global Mars dust storm from 2001 )

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Technically, private space could send one way missions that contaminate Mars without triggering this legislation to protect Earth’s environment. And if Laura Montgomery’s view on the US interpretation of the OST prevailed, and if Congress was to legislate in their favour, perhaps US citizens could go ahead and land materials there without doing anything to protect Mars.

For instance, Elon Musk wants to put some assets in place for the astronauts to use later on, in his first unmanned missions to Mars. He could send a BFR to Mars as soon as the rocket exists. He could send something there already on his Falcon Heavy, had plans for a “Red dragon”, if he dusted off those plans he could land a Dragon capsule on Mars in the near future.

But the astronauts, if I’m right here, are not going to be able to go to Mars until the astrobiological survey is done. So there is no hurry to land their habitats on the surface.

Indeed, if the survey took a decade, as it well might, the habitats would be technology at least a decade old by the time they got there.

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Some keen Mars colonization enthusiasts might at first welcome the idea of sending Earth life to Mars, even intentionally - thinking, that (in their view) it improves Mars to introduce Earth life there - and that if we contaminate Mars, even make it as dirty as possible with Earth microbes, that’s an end to the planetary protection provisions.

Wouldn’t it mean that we don’t need to take any more precautions? It is now contaminated, so just land and forget the orbital survey.

Well, even then, if some Earth life has got to Mars, it doesn’t mean that all possible Earth life has got there. Early settlers in Australia had already introduced the feral pig and horse by the end of the eighteenth century. But it still would have been worthwhile to keep out the water buffalo, goat, camel, cat, red fox, rabbit, donkey and cane toad, as well as many other invasive plants, insects etc. Invasive species in Australia - Wikipedia

Also it would do nothing to protect Earth or make Martian life harmless to Earth.

We would still need to do a proper astrobiological survey before returning materials from Mars to Earth, and it wouldn’t make any difference to this requirement.

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If we add Earth microbes to Martian microhabitats it gets harder to isolate any native Martian life, to learn what it’s unique properties are, and to determine whether it is safe for Earth’s environment or for our astronauts. It might well mean it takes longer to complete the survey.

That’s especially so since some of our life detectors may have a bias towards detecting Earth life. For example, we may well send a gene sequencer as part of the payload. We now have miniature end to end gene sequencers small enough to hold in your hand - and the SETG project to send one of these to Mars is at a reasonably advanced state of technological readiness.

If we did that, it’s optimized for Earth life, so would find Earth originated DNA and RNA easily. But what about RNA world cells, with no DNA? Or even “non chiral” RNA - all Earth life uses RNA spiraling the same direction. But extraterrestrial life could use Joyce's ribozyme to replicate using a mix of mirror image RNA together with normal RNA in the same cell (one of the many suggestions for very early life).

Or, suppose, mixed in with it, there is another unfamiliar biopolymer such as PNA, or TNA (like DNA with a different backbone), or a hodgepodge mixing different backbones in the same molecule? It would not spot a thing.

When you have no idea what, or even if there is any extraterrestrial life in the mix, it can’t help but make your task harder to have a lot of terrestrial DNA in it from forwards contamination. However, the life that you can’t detect would be no less hazardous for being mixed with Earth life.

Indeed, anything that survives in the mix, after forwards contamination by Earth life, is potentially native Martian life that could compete with Earth life on at least equal terms. This means it could substitute for Earth microbes in our biosphere, but possibly behave differently and modify the Earth’s biosphere.

So we have to detect any such life, to evaluate whether it is an issue for Earth if it gets here, what difference it would make to Earth’s biosphere if some of the microbes are partly or completely substituted for by their Martian analogues, and if so to take whatever measures are needed to keep Earth in good condition.

There’s also the possibility of native Martian life exchanging genetic capabilities with introduced Earth microbes, making Mars a breeding ground for possibly hazardous life for Earth. It could make it more biohazardous than it was.

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We also have no idea what Earth life would do to Mars, in the unusual conditions there. It will encounter conditions that are not exactly like any that we have on Earth - but possibly still habitable to Earth microbes. The previous planetary protection officer, the biologist Cassie Conley gave a simple example to show how we could get an unpleasant surprise if we introduce microbes inadvertently without knowing all the interactions and what they could do there. These interactions could cause harm even if Mars is lifeless.

Some Earth microbes, in the anoxic conditions on Mars and in the presence of methane (which may well be present there), could form calcite in underground aquifers - so turning them to cement.

"Conley also warns that water contaminated with Earth microbes could pose serious problems if astronauts ever establish a base on Mars. Most current plans call for expeditions that rely on indigenous resources to sustain astronauts and reduce the supplies they would need to haul from Earth."

"What if, for example, an advance mission carried certain types of bacteria known to create calcite when exposed to water? If such bacteria could survive on Mars, Conley says, future explorers prospecting for liquid water instead might find that underground aquifers have been turned into cement."

Going to Mars Could Mess Up the Hunt for Alien Life

In more detail, Mars has almost no oxygen, which changes how microbes behave. What she is talking about there is anaerobic oxidation of methane, which leads to the formation of calcium carbonate in anoxic conditions . It's done by a consortium of methane oxidising and sulfate reducing bacteria. See summary here in wikipedia: Calcite - formation process - which links to this technical paper which goes into more detail.

Calcite - calcium carbonate. In the anoxic conditions on Mars, in presence of methane, a combination of methane oxidizing and sulfate reducing microbes can cause calcite to form and so, basically, could turn underground aquifers on Mars into cement. Cassie Conley’s example of one way that accidentally introduced microbes could have unpredictable effects on Mars.

When it comes to microbes introduced to an unfamiliar planet that behaves differently from Earth, with many differences in the chemistry, atmosphere, environment - any number of unexpected interactions could happen.

It may be important for our future to map out some of those interactions, and if undesirable, see what can be done to avoid them, BEFORE they happen rather than try to fix what happened after the event.

Microbes from Earth can also mutate on Mars. They would encounter conditions never encountered before on Earth throughout their entire evolutionary history. The ionizing radiation will increase the mutation rate too; they can also recover hidden capabilities through changes in gene expression. If there is native Martian life and it is related, Earth microbes can also take up capabilities from Mars microorganisms via lateral gene transfer, even perhaps if it is unrelated but uses DNA / RNA. This could lead to new pathogens that would endanger the astronauts too. Quoting from Conley and Rummel's paper

"Given the assumption that there really will be a serious effort to go to Mars with humans and have them do things on the surface, we can posit that human missions will inevitably bring a large population of Earth microbes along with them. We should anticipate, too, that not all of those microbes will always be harmless. If humans are going to contaminate Mars, we also need to be concerned about the possibility that the microbes they carry could endanger the astronauts, both in their native state and if they mutate in the space environment. If Earth life and Martian life are related, or if Martian life is unrelated but still uses DNA/RNA, then lateral gene transfer is another route for acquiring new (and potentially hazardous) traits. While COSPAR planetary protection policies are principally science-enabling, they have other benefits as well."

(Emphasis mine)

(see also my Let's Make Sure Astronauts Won't Extinguish Native Mars Life - Op Ed )

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This would also be an issue with an attempt to treat with the Martian materials “hazmat style” in an early human mission to Mars before completing the survey.

Yes, it might be possible, with vastly added complexity, to keep Martian dust out of the habitat, even the fine dust in the air, so long as none of the astronauts nicks their glove or spacesuit. Perhaps, especially in a short “flag and footprints mission” this could be feasible.

However, to contain it both ways, to prevent forward contamination of Mars as well is not just challenging, it is impossible (apart from the unlikely option of landing a human in a crash proof metal sphere which they never leave and the sphere is then returned to orbit and sterilized on the outside with them still inside it).

the thing that makes forward contamination impossible to prevent on Mars is there is a high chance of a Challenger type crash with the spacecraft and crew and debris spread over thousands of square kilometers of Mars. That is irreversible contamination of Mars and no question about it and the risk of that happening could be as high as 50% with early missions to the Mars surface - it is also a reason in favour of telerobotics for safety reasons.

Even if it was just 1 in 20 like the space shuttle that's an unacceptable level for preserving the science interest of Mars

In particular, if you have humans land on Mars, you have a possibility of the human mission crashing on Mars and after a Challenger type crash with debris spread over thousands of square kilometers, that would be an end of protection of Mars from forward contamination.

So, an attempt to land humans on Mars before you do an astrobiological survey has potential to confuse the situation there, so that the survey lasts longer.

For more about these possibilities and many more, I have a section in my Touch Mars? book:

In this way, it is of benefit to prospective colonists too, to get this astrobiological survey done properly and promptly.

Have any of the keen advocates of near future human missions to Mars drafted out provisions to break this chain of contact with the Mars surface during a human mission to Mars? Well not that I know of. As usual do say if you know of anything in the comments.

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I’m not sure. Perhaps they expect it to be like Apollo, and assume that the quarantine facilities for Apollo for humans showed how you'd do it? But as we saw, it is now though to be mainly of interest for showing how not to do it and as completely inadequate for protecting Earth's environment. It has also been rescinded long ago.

The matter is raised in workshops on manned missions to Mars, but - surprisingly - those also use the Apollo model, of quarantine. The focus their attention on diseases of humans with a reasonably short latency period. They rely on the crew watching out for symptoms during the mission. If they get unexpected symptoms they would then attempt to attempt to determine if they are due to Martian pathogens, or perhaps the unusual Martian soil chemistry, or a terrestrial pathogen.

As Cassie Conley put it, interviewed by

"They're going to have runny noses, they're going to have some skin rash. People who are in a small, contained environment for hundreds of days — that happens to them."

“Astronauts should assiduously track the nature and severity of these various illnesses as part of their concerted health-monitoring efforts, with one crewmember assuming primary responsibility for implementing planetary protection protocols throughout the entire mission”

"Six people going on a mission to Mars — if something happens to them, that's a really bad tragedy and we want to prevent that as much as possible. But six people bringing some horribly infectious, horribly damaging organisms back from Mars to Earth is a global tragedy, and there is a difference in scale there that has to be recognized." Will Sick Mars Astronauts Be Forbidden from Returning to Earth?

See also: Report on the COSPAR Workshop on Refining Planetary Protection Requirements for Human Missions (try a search of the text for “quarantine” for the relevant passages).

If you go to the COSPAR guidelines they give as their main precaution for a human crew:

A quarantine capability for both the entire crew and for individual crew members shall be provided during and after the mission, in case potential contact with a Martian life-form occurs.

Meaning: Detailed formulation of quarantine needs and capabilities will need to be determined on a mission - by - mission basis, in consultation with relevant experts and agencies on the basis of the best available scientific advice and understanding of risks. Appropriate technologies for quarantine and containment of crew and samples will be needed for both nominal and off-nominal situations. As part of normal crew health monitoring and in support of the assessment of possible quarantine measures, basic tests of the medical conditions of the crew and their potential responses to pathogens or adventitious microbes will need to be employed regularly on the mission.

COSPAR Planetary Protection Policy of October 2002, as amended to March 2011 (annotated version)

This would spot some things of course. For instance it would spot an attack of a biofilm on the lungs if it happened as rapidly as Legionnaires’ disease, which takes a few days to develop symptoms.

And if they suspect a Martian pathogen, presumably they would stay within a quarantine facility until the disease has run its course - or do they leave quarantine and go to hospital? Do they stay in the facility for the rest of their lives in that event? This was never fully worked out for Apollo as far as I can tell, what you do if the astronauts get sick. The underlying assumption seems to be that the crew won’t get sick.

As far as I can see none of these papers or reports address the question of a possible multi-year latency period, as raised by Sagan with his example of leprosy and its latency period of over a decade (can be 20 years).

They do go on to talk about a comprehensive planetary protection protocol that deals also with sample handling and return of samples and crew to Earth

A comprehensive planetary protection protocol for human missions should be developed that encompasses both forward and backward contamination concerns, and addresses the combined human and robotic aspects of the mission, including subsurface exploration, sample handling, and the return of the samples and crew to Earth.

Meaning: Building on studies and protocols from other round trip and sample return missions (e.g. Apollo, Mars Sample Return, etc.) a protocol for handling, testing and assessing returned humans and samples will need to be developed, incorporating the most up-to-date science, technology and operations during all mission phases. Mitigation capabilities and strategies will also be needed in the event of off - nominal releases of contamination during various mission phases .

COSPAR Planetary Protection Policy of October 2002, as amended to March 2011 (annotated version)

But again this is very sketchy. In the forwards direction they recognize that Earth originated extremophiles can get to Mars despite the preliminary sterilization, and UV on sunlit surfaces, the vacuum of space etc.

But in the reverse direction, the requirement for a rock returned from Mars is that even release of a single spore, even a particle 50 nm in diameter, is considered to be unacceptable under any circumstances. How is that supposed to work for humans returning in a spacecraft that’s been exposed to the dust in the Martian air? And the Martian microbes possibly joining the personal microbial clouds of the astronauts?

They would have to work through this for a detailed impact assessment similar to the detailed studies we have already for a robotic sample return. As far as I know this just hasn’t been done yet.

In summary the discussions of the precautions for a human mission to Mars seem to be at an early stage so far. The studies cover topics in a few sentences, with lists of knowledge gaps, when comparable robotic sample return studies run to books of several chapters on the same topic.

All this would surely have to be examined in great detail during the public discussions and the legal processes needed before such a mission could go ahead. This time, answers would be required, not a list of knowledge gaps, before a mission could be approved. Especially given the gravity of what could go wrong for the worst case scenarios.

As usual, please do say in the comments if you know of such a study - or if I am missing something in this analysis.

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One objection you often hear is that we need to return the samples to Earth before we can detect biosignatures at all. But this is not true. Even in the 1970s, the two Viking landers had biosignature detection instruments. They were confused by the unusual Martian chemistry. But if they had encountered chemistry similar to Earth deserts, they would have been able to detect at least some forms of Martian life reasonably conclusively. The scientists concerned started to design follow up missions that could still detect biosignatures without being confused by the unusual chemistry there but they were never sent.

Since then, technology has moved forward at a tremendous pace of course, and we have miniature instruments that are vastly more capable than the Viking ones.

The progress in the instruments designed by astrobiologists in the past decade has been just astonishing. Many instruments that covered a lab bench or even filled an entire lab are now “labs on a chip” weighing a few kilograms and with power requirements in watts. None have yet flown, but a couple did get onto payload manifests, ready to fly, but were descoped.

Typically most of them would not be enough to confirm life by themselves. However, as for Viking, you would send a suite of several of them and multiple biosignatures would be a good sign that you do have life there. The instruments are far lower mass, less power, more capable, and so we could send many more instruments for the same payload than for Viking.

Some of them would be definite proof, e.g. if you see a microbe swimming in an optical microscope. That’s not impossible with a holographic off field microscope that lets you do the focusing after you take the photograph - or if you can concentrate the microbes into a smaller region.

For most of the instruments, as for Viking, you’d aim for multiple simultaneous detection of different biosignatures. Also, you would plan for follow up missions. It’s a big ask to expect to be able to detect an alien biochemistry unambiguously with the first ever experiments sent to the habitat. After the first data comes back, of course you need to plan for a follow up mission - and indeed eventually sample returns (perhaps to above GEO for optimal protection of Earth and yet easy of access for telerobotic experiments from Earth with future heavy lift capabilities). But first you have to find it.

Astrobiologists strongly advocate for searching for life in situ first. If life is very abundant there, then we may find it right away, in the dust. But if not, it might take a while to find it.

  • Mars has a constant influx of organics from interplanetary dust, comets and meteorites. These can sometimes mimic biosignatures too, such as chirality imbalances and enhanced quantities of light isotopes.
  • In extreme habitats like that, life is often patchy, and has low concentrations of organics - Mars 2020 could drill for a sample just cms away from a patch of life and not know it.
  • The ionizing radiation erases any signal from surface organics over hundreds of millions of years, destroying even the amino acids.

For these and other reasons, all the papers by astrobiologists that I've read say that returning samples for analysis is a costly and inefficient way to search for life there. It is much more useful for geology. They expect the samples returned by Mars 2020 to be as ambiguous for the search for life as the Martian meteorites we already have, and the same would be true for samples returned telerobotically to orbit, unless they have found signs of life on Mars already. I cover this in detail in my section: Astrobiologists advocating strongly for an in situ search on Mars first in the book.

Also in

If you want to skip to the next section go to Yes - robots can drill on Mars - exomars will, as will insight lander

Here is a trimmed down summary of the main methods:

So, the idea is to send a suite of several such instruments. If many of them detect life you can be pretty sure it is there. And if they don’t, a null result is also of great interest for the search for life. Indeed, discovery of pre-biotic chemistry is also interesting, especially if there is no life in an apparently habitable brine on Mars.

Preliminary testing with laser light

If you shine laser light at the sample (not zap it, just gently light shining on it) - can give some information right away through Raman spectrometry. This technique works by analyzing a tiny fraction of the light (1 in 10 million) that interacts with the surface as it bounces back.

This technique is sensitive, and able to detect organics and some biosignatures. One of its best features is the way it can measure the distribution of the organics and other compounds by pointing the laser at different points on the surface - and is non destructive so it can be applied first before any of the other tests.

Amongst other targets, it could perhaps spot biosignatures that microbes use to protect themselves such as beta-carotene (UV protection) or glycerol (low temperature protection), both of which are targets of Raman spectrometry on Earth.

It works great for some materials, e.g. gypsum. For other materials such as clays it can give less clear results, making it harder to identify the specific molecule, confused by transition metals in the clays. See this thesis by David Hamilton in 2016

Mars 2020 and ExoMars both will use this method.

Detecting trace levels of organics:

Search for life directly by checking for metabolic reactions

These can detect life even if it doesn't use any recognized form of conventional life chemistry. The life only has to metabolize - “eat something” - doesn’t have to have to reproduce. That makes a big difference as the microbes might take months to reproduce if they are cold loving, and only 1% of microbes on Earth can be cultivated anyway - it may be harder to cultivate Martian life if anything.

  • Microbial fuel cells, where you check for redox reactions directly by measuring the electrons and protons they liberate.
  • Levin’s idea of chiral labeled release, where he has refined it so you feed the medium with a chiral solution with only one isomer of each amino acid. If carbon dioxide or methane is given off when you feed it one isomer and not with the other, that would be a reasonably strong indication of life.

Electron microscope

  • Miniaturized scanning electron microscope. This can’t detect whether it is life or not, but is useful along with the others for examining tiny structures. It is able to do chemical analysis as well as imaging.

Optical microscopy

Raman microspectroscopy. Combines an optical microscope with a laser shining light on the same microscopic cell observed by the microscope and the scattered light is analyzed as for normal raman microscopy.

Very promising but in a paper "Implications for the search for biomarkers on Mars" (page 3219), the authors found that focusing on microbial colonies can be difficult and time consuming, needing precise work, even when the microbes were common enough so that you could see them as a "clear greenish zone on the macroscopic scale.

Atomic force microscopy

This can measure the forces between molecules and properties of cell walls such as elasticity, hardness etc (page 4-26 of Europa lander report). This is mature space technology that has flown on the Phoenix mission to Mars and the Rosetta mission, though it's not been used to search for life.

Using an optical microscope to watch microbes swimming

See this paper: Microbial Morphology and Motility as Biosignatures for Outer Planet Missions

The smallest microbes are too small to swim because they get jostled about too much by brownian motion (the jostling of molecules hitting them). But microbes can swim if they are larger than 0.6 microns, and we often see microbes larger than 0.8 microns swimming on Earth. Also, they are often mobile even in very cold dry conditions on Earth.

The main problem again is focusing on them to find them. There is a solution though, holographic (interferometric) microscopy. Diffraction limited, but you do the focusing after capturing the light, digitally. No mechanical moving parts, and it can be operated without user input to focus the microscope. The authors of this paper: A Submersible, Off-Axis Holographic Microscope have developed such an instrument with 800 nm resolution which can be used underwater. They were able to observe active prokaryotes in sea ice.

Using an optical microscope to watch fluorescing microbes

This again is from Microbial Morphology and Motility as Biosignatures for Outer Planet Missions. Shine UV light on the microbe and see if it shines with visible light. All microbes do this to some extent and some pigments, especially chlorophyll, absorb UV and emit strongly in visible light.

Also, deep UV at wavelengths less than 250 nm can make the aromatic amino acids autofluoresce (i.e. the ones that incorporate a ring of six carbons).

You can also use fluorescent dyes that attach to nucleic acids, lipids, cell walls, and other biosignatures. The dyes may be unstable at high or low temperatures and are complex organics, introducing those to another planet could have planetary protection issues (teaching native life “new tricks”)

Near field scanning optical microscopy

This technique is mentioned in "An Astrobiology Strategy for the Exploration of Mars ", page 72.

"Other imaging technologies including interferometry, scanning near-field optical microscopy, and electron microscopy techniques should also be developed for spaceflight applications."

This gives optical images that are higher resolution than 0.2 microns, below the diffraction limit, using evanescent waves. The detector has to be very close to the object being observed, at a distance less than the wavelength of the light. This is an example of its use for fossil microscopy combined with Raman microspectroscopy.

Direct search for DNA

DNA sequencers have shrunk more than any other instrument in the list. Once filled entire laboratories. Now small enough to send on a spaceship. The focus so far is on DNA but it's possible to sequence RNA based life too- so long as it uses the same bases as on Earth. Sequencing for life based on other non standard bases is also possible but work in progress, see the paper for the techy details.

So it does depend on the life being similar - on the other hand if no DNA is detected that tells you something too.

One issue is the vast amount of data in a sequence, it can be up to 1 TB raw data in a large sequence. They can reduce that by processing a lot of it in situ, but still likely to return, for instance, 44.2 GB of data for a 22 billion base sequence. That's equivalent to 22 images of the Mars Reconnaissance Orbiter's HiRISE camera. Less for smaller sequences of course.

But with broadband communication back to Earth, no problem.

(A trimmed version of my more detailed descriptions here: In situ instrument capabilities (in Touch Mars?)

Search in situ for multiple biosignatures for an unambiguous detection

Once you have unambiguous biosignatures you can return samples to orbit and then they can analyze them in telerobotically operated facilities. It is a case of doing it that way because you have to, until you know what is there.

Eventually as we find out more, we can learn how to handle it safely, and may be able to return it to Earth or to facilities inside the orbiting spacecraft around Mars. We may need to take special precautions, or none at all.

If astronauts are exploring the Martian surface robotically and eventually find life there, they will send samples up to orbit for analysis, much in the way they would return them to a habitat on the lunar surface. The big advantage here is that they get to analyse the samples, perhaps even within days of collection, within months at least. This could be especially important if the samples contain viable life that is challenging to cultivate in a laboratory - or if the sample has volatiles that can be lost easily.

However, until they know what it is they are studying, they wouldn’t examine them inside the crewed vehicles. They would study them inside separately flown modules not attached to any spacecraft, using telerobotic equipment. At least, they would do this, until they establish that it is safe for themselves, and Earth to study them in their habitat - if they do establish that.

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This is often raised as if it is a fatal objection, that only humans can drill. But in the conditions on Mars, then it is dry drilling, no drilling fluids. You can’t take drilling casings with you unless very narrow as they’d be too heavy.

But, as we touched on, in those conditions robotic self hammering moles are ideal. And those can be deployed from a rover just fine.

The regolith on Mars is reasonably soft and extends to a depth of 5 meters or more over much of Mars. Two meters is deep enough for relatively undamaged organics. A few centimeters is fine to reach the near subsurface brine layers.

There is no reason why we can’t drill for tens to hundreds of meters and Honeybee robotics are optimistic that their autonomous “inchworm” can drill kilometers.

For more on this see my last article under:

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One concern - if we are sending rovers to dozens of locations on Mars and they are actually going to contact liquid brines close up - is that even if sterilized to Viking standards, they may introduce Earth microbes to Mars. The chance is likely to be low, but on the other hand of the few remaining viable spores, the sterilization process favours survival of polyextremophiles, and if we can eliminate the risk altogether, so much the better.

This is a personal view, I happen to think that we should as a top priority work on developing 100% sterile rovers to explore Mars. This is something we can consider now, which was not within our capabilities for Viking in the 1970s. We have all the components of a rover able to operate at 300 °C , either as commercial equipment, or worked out as part of a project to develop a Venus surface lander. It is still a major challenge to build a rover capable of working at the 500 °C of the Venus surface. But we only need 300 °C to destroy all amino acids during the months long cruise out to Mars. That we can do already with the existing equipment and the designs for a Venus actively cooled rover at 300 °C. Indeed the requirements are less strict, because our rover doesn’t have to operate at 300 °C, it has to survive in those conditions but will operate at normal temperatures once it arrives on Mars.

You often hear people say that we can’t sterilize our rovers to the extent they could for Viking because the components are so much more sensitive to heat. That is true if you base your rover on commercial equipment developed for use at normal room temperature. But there are also these commercial devices developed for 300 °C and those are far more heat tolerant than the Viking equipment.

This is something we could work on in parallel with the work to develop surface rovers to Venus - and the result would be a complete rover that can be 100% sterile and used anywhere in the solar system, including, for instance, Europa, Enceladus etc. Even send robotic submarines into the Europan near surface iced over lakes and subsurface sea without any concern about forwards contamination. Also to do the same in Antarctica with lake Vostok etc.

The initial outlay would be high, to build and certify the first rover, and to develop ways to port life detection instruments to this new capability as well. But the payoff from this technology would be huge, never needing to be concerned about forward contamination again in life detection missions throughout the solar system.

I covered the techy details, with cites, in this section of my previous article:

It’s also covered in my Touch Mars? book.

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This shows how far we have moved forward in the way we value Earth’s environment since the 1960s. It is no longer acceptable to take risks of harming it in a major way, even if the chance is small.

But studying Mars from orbit via telepresence is not only totally safe for Earth’s environment, and far safer for Mars in the forward direction. It is also a faster way to do an astrobiological survey of Mars.

If we had Elon Musk’s BFR particularly, then for a cost not that different from a single decadal flagship mission today, we could land tons of equipment at each of a dozen different landing sites on Mars. If those tons include numerous tiny sterilized rovers, then we could have a great first astrobiological survey of Mars quickly. The very first mission to Mars could transform our understanding. It would be bound to leave some unanswered questions, and the next one or the one after that would answer most of those,while of course raising more questions.

It is a very exciting mission for an astronaut, in orbit around Mars, exploring it via telepresence, in effect, they are in orbit in a shirtsleeves environment in a spaceship probably with a counterweight (perhaps another BFR) and tether for artificial gravity. No need for all the very tedious process of donning a spacesuit. Have your morning breakfast and coffee, go over to the telepresence work station and right away you are there on the surface of Mars in your mind, looking around with 3D binocular vision, able to pick things up with haptic feedback so you can touch things

Probably also you have an omnidirectional treadmill you can use if needed to move the rover around on the surface just by walking in whatever direction you want to move. Omnidirectional treadmills used to be huge monsters of a device but with the influence of computer gamers they are now small and can easily be included in a spaceship.

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If we decide we shouldn't send humans to the Mars surface quite yet, but want to go one step further than robotic exploration from Earth, and send humans there, there are many exciting missions we can do to the Mars system. We can explore Mars by telepresence from orbit, or from its moons Phobos and Deimos, or in flyby missions (using Mars as a gravity assist to get back to Earth)..

As for the duration of the survey, well, we can't know in advance. We might know some things quickly. It might be a matter of luck, too, do we find life right away, or does it take time? What kind of life is it, if we find it? As the survey continues, we'll have new questions that need to be answered, to determine whether Mars life is safe for Earth, or Earth life for Mars, and how the two biospheres are likely to interact, if there is a distinct biosphere on Mars. But we need to start the search before we can begin to map out the most important questions that need to be answered, and how best to answer them.

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Telerobotics lets us explore Mars much more quickly with humans in the loop. The early stages of telerobotic exploration of Mars would use an exciting and spectacular orbit if we follow the HERRO plans. Every day the Mars space station would come in close to the poles of Mars, swing around over the sunny side in the equatorial regions and then out again close to the other pole, until Mars dwindles again into a small distant planet - and not only once. It does this twice every day. This "sun synchronous" orbit always approaches Mars on its sunny side so you get to see both sides of Mars in daylight from close up, every single day.

Imagine the view! From space Mars looks quite home-like, and the telerobotics will let you experience the Martian surface more directly than you could with spacecraft. You'll be able to touch and see things on the surface without the spacesuit in your way and with enhanced vision, and adjust the colours to show a blue sky also if you like. It's like being in the ISS, but orbiting another planet.

12th April 2011: International Space Station astronaut Cady Coleman takes pictures of the Earth from inside the cupola viewing window.- I've "photoshopped" in Hubble's photograph of Mars from 2003 to give an impression of the view of an astronaut exploring Mars from orbit.

This is a video I did which simulates the orbit they would use. I use a futuristic spacecraft as that was the easiest way to do it in the program I used to make the video. Apart from that, it is the same as the orbit suggested for HERRO.

(Click to watch on YouTube)

It would be a spectacular orbit and a tremendously humanly interesting and exciting mission to explore Mars this way. The comparison study for HERRO, completed in 2013, finds that a single orbital mission for a crew of six does more science than three similar missions on the surface, for far less infrastructure and only a little over a third of the total number of launches (you don't have to land the large human rated habitats on the surface of Mars) Here is a powerpoint presentation from the HERRO team, with details of the comparison. This is their 2011 paper and this is their 2013 paper on the topic.

Then, if you have humans orbiting for Mars, then for sure, you'd also have broadband streaming of everything back to Earth from Mars. As well as being very safe, also comfortable for the crew, you'd also have wide-field 3D binocular vision, which we can all share at home back on Earth.

It's amazing what a difference this makes, I recently tried out the HT Vive 3D recreation of Apollo 11. We'd have similar 3D virtual reality experience of the Mars surface. It would actually be a much clearer vision than you'd have from the surface in spacesuits, digitally enhanced to make it easier to distinguish colours (without white balancing the Mars surface is an almost uniform reddish grayish brown to human eyes), and so that we can see bright colours even as it gets dark, and indeed, with false colour you could see ultraviolet, infrared etc as well if you want to.

Here is a hololens vision, which though it's not telepresence, I think gives a good idea of what it might be like for those operating rovers on Mars in real time from orbit, some time in the future with this vision.

(Click to watch on YouTube)

And not only that. Everything you see on the Mars surface is streamed back to you via broadband of course. This means it can also be streamed right back to Earth. We will definitely have optical broadband between our Mars missions and Earth by then. There was proposal to do this in the early 2020s with a mission that would have streamed back 100 gigabytes a day, over 4 gigabytes an hour.

By then it will surely be gigabytes a minute or faster.

This means though, that we can build up copies of the 3D landscape back on Earth as you explore it and experts on Earth can walk into the very landscape you are in on Mars, and inspect the rocks, from all angles (if you have walked around them previously so that they have seen all sides). With multigigabyte images they can also be high enough resolution for scientists to study them close up as if they were looking at them with a geologist’s hand lens, higher resolution than you can yourself unless you choose to do the same while navigating in VR from orbit.

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The HERRO study mentions this briefly, but I think it is worth going into it in detail as it is a major advantage of telepresence exploration. There is no need to suit up, which currently is a long procedure. Astronauts on the ISS start preparing for an EVA, the day before, checking out the airlock and their spacesuit to make sure everything is in order, camp overnight in the airlock, and spend hours preparing for the EVA the next day too.

Here it’s easy to get confused between the spacesuits used for EVA’s and the IVA suit - which is only used to save an astronaut’s life in an emergency. Of course they have to be able to put on an IVA quickly, and don’t spend days preparing for it.

This is a lightweight suit, uses full pressure inside, usually has an umbilical to the spaceship’s life support though it may have some tens of minutes of inbuilt air supply too, and is meant to save your life and give you some mobility in an emergency.

Elon Musk’s “Starman” wore an IVA suit when he launched the red Tesla in roughly the direction of Mars orbit.

SpaceX’s IVA suit

You can don an IVA quickly in an emergency. Astronauts will also put them on and keep them on all the time during critical maneuvers such as a docking, or re-entry. But if the pressure around you reduces all the way to a vacuum, your mobility will be severely reduced.

Their aim is to have some flexibility so that you can get out of a chair and operate some of the instruments.

(Click to watch on YouTube)

For more on this see my answer to What is your opinion on Elon Musk's SpaceX spacesuit?

If you want to go out of your spacecraft or habitat, with an independent air supply you carry with you, and you want the mobility to be able to work in the vacuum of space or the near vacuum of the Martian surface, that’s when you need an EVA suit, like the ones used by the Apollo astronauts and the ISS astronauts on space walks. That’s when it gets really complex. These things are like miniature spacesuits, and they are also operated at reduced pressure for mobility.

You sleep in the airlock the night before, as the pressure is gradually reduced. That's because the EVA suits would be so stiff if you filled them with Earth normal pressure atmosphere, that it would be almost impossible to move your fingers.

To make this possible, they use pure oxygen, which lets humans breathe and be comfortable at a much lower pressure of 30% of air pressure at sea level on Earth. However, they don't want to keep the entire ISS at such a low pressure, as a pure oxygen atmosphere is a fire risk. Given those decisions, the only solution is for the crew who are doing the EVA to adjust to the lower pressure for every EVA, which they do by this procedure which they call "camping out" or sleeping overnight in the airlock. They have to do this slowly or they risk suffering from “bends” as the nitrogen they breathed in dissolves out as gas bubbles in their blood, a potentially serious effect.

Piers Sellers (left) and David Wolf using pre-breathe exercises to purge their blood of nitrogen to prevent "bends" as they adjust to a third of Earth's atmosphere and a pure oxygen environment. This is done the day before the EVA and they "camp out" overnight in the airlock ready to exit for their EVA the next day. This photo was taken during the STS-112 mission on 10 October 2002. (Image: NASA). For details see page 4 of this article.

That's the main difference between the ISS and Apollo. The Apollo mission used a pure oxygen atmosphere pressurized to five pounds per square inch, so 34% of Earth normal. That’s why they could get into their spacesuits so easily - though you are still talking about over an hour to don an Apollo spacesuit (it took them an hour to do it on the ground with many other technicians helping them because the spacesuits are so heavy in ground conditions).

The Apollo oxygen atmosphere was a fire risk, as they knew from the Apollo 1 fire, and originally NASA awarded North American Aviation (NAA) a contract for a mixed gas environment, but they then changed that back to pure oxygen, because a mixed gas would add to the mass of the mission.

NAA continued to argue for the mixed gas, but NASA argued for oxygen which they had already used successfully with four Mercury missions, on the basis that at a third of Earth pressure, the risk from fire is much less and within the capability of a well trained crew to manage it, if they took care also with construction of the spacecraft with few flammable materials.

You might wonder why it's an increased fire risk when the partial pressure of oxygen is the same as on Earth. The reason is that nitrogen is a fire retardant, slowing down or stopping the spread of fires by absorbing some of the heat in the fire. The level of oxygen we have on Earth is already high enough so that, for instance, forest fires start quite easily. We'd have many more fires if it wasn't for that naturally flame retardant nitrogen.

A thinner atmosphere with the same amount of oxygen but no nitrogen is much slower at taking heat away from a flame or smoldering ember or a wire that is heating up too much, and so there is an increased fire risk. It is not nearly so bad as for Apollo 1 of course which had oxygen at Earth normal pressures, but the risk is high enough so that they took care with Apollo to reduce the amount of flammable material inside the spaceships as much as possible. Even after doing that, they still recognized that it was an increased risk that they countered by having well trained crew.

Then, as I said in the intro, even with a third of Earth's atmospheric pressure inside, the suits are stiff and difficult to use, especially the gloves. Like having your fingers inside a garden hose.

When astronauts walk around, they are not flexing cloth as they move. They are not like movie spacesuits.

The outwards pressure of a third of an atmosphere makes the material totally stiff like a high pressure balloon. The whole thing is, though made of soft materials, basically rigid except at the joints which are bearings with air as the lubricant in between constantly flowing out - that's how all spacesuits have been made to date, the Apollo ones and also the Russian and US ones for the ISS. You can't tape up the joints as you can with a HazMat suit. In the case of the Apollo astronauts they could turn around at the waist but they couldn't bend forwards which is why they often resorted to controlled falls to pick things up. Same for the ISS astronauts. They can't bend at the waist inside a spacesuit. There just isn't a way to devise a spacesuit with bearings that lets you bend at the waist as far as I know, so that's likely to be the same for a Mars suit or a new Moon suit too.

A pressurized suit is a forwards contamination issue too. You can't do anything about the possibility of forwards contamination during a crash so perhaps this is an academic issue. We wouldn't have humans on the surface anyway unless we have decided we no longer need to be concerned about irreversible eventual forwards contamination of Mars.

But if we use gas pressurized spacesuits for Mars, similar to those used on EVA's in space so far, then one estimate is that over 50 litres of oxygen with human borne bacteria and other airborne effluent would escape through suit bearings and joints during each EVA, potentially contaminating soil, fossil and atmospheric samples. 50 litres may seem a lot but it's not much compared with the total amount they breathe in an EVA. But a lot of air for microbes to get out on. See this paper. There is an outer Thermal Micrometeoroid Garment outside of all the joints but presumably this is made so that it can leak. Otherwise it would fill up and pressurize like the inner suit and be impossible to flex.

Mechanical counter pressure suits may help with the mobility issues. It's a nice idea, currently being explored by Dawa Newman at MIT.

(Click to watch on YouTube)

Longer video here

(Click to watch on YouTube)

But they have some disadvantages too. The elasticity makes it hard to don and doff the suit, it's difficult to maintain the counterpressure in all postures, it also gives no convection to warm or cool the body, and it has to be tailored to each crew member and maintain a "second skin" fit throughout the mission, through any changes in their bodies. It's particularly hard to tailor them to hands and they normally use gas filled gloves, and boots, as well as the helmet (though they do hope to use them for gloves eventually too). That's from the section on mechanical counter pressure suits here:  "Risk of injury and compromised performance due to EVA operations".

Our current spacesuit designs are tough on the wearer and cause many minor injuries, including blisters, sore shoulders, pinched nerves, loss of fingernails, etc, with a total of 219 injuries or a little over one per EVA. That includes 9 with the Apollo surface EVAs. For more on all this see this 2015 report: "Risk of injury and compromised performance due to EVA operations".

Then they also need a lot of maintenance. The Russian Orlan is discarded after 12 uses and the US EMU is returned to the ground for refurbishment after 25 uses. Unless the Mars suits are far tougher than this, eventually after a dozen or a couple of dozen EVA’s, you need a new spacesuit from Earth.

It's possibly sooner on a planetary surface; the lunar suits were filthy with the lunar dust and in a pretty bad way after three EVA’s. Sometimes one or the other crewmember could not do the final fourth in orbit EVA to retrieve the camera from outside of the lunar module because the oxygen leakage rate was beyond the tolerance level. If they can be used longer term on Mars they are likely to require a lot of maintenance between every EVA.

Soft robotics may help with spacesuit gloves - they may also help with the telerobotic rovers.

(Click to watch on YouTube)

Yes, for sure, future redesigns are bound to improve the spacesuits so they are less stiff, easier to use and require less maintenance and last longer. But at the same time, the technology for telerobotics will improve as well. Also the need to maintain suits between EVAs, do numerous safety checks, and pre-breathe for an hour or more before an EVA seems likely to be with us for some time into the future. There seems to be no prospect in the near future of a flexible EVA suit you could just don and go out of your habitat with as easily as in the movies.

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A fire is one of the most dangerous things that can happen in space, more dangerous than on Earth. There is nowhere else to go to escape from it, and it might not be easy to purge the atmosphere of smoke and carbon dioxide if the spacecraft itself is on fire. You can’t just open a window to let out the smoke and stale air.

They could use oxygen for rover, for a field trip of a few days or even a week or two. That makes sense, more like Apollo. Make sure nothing is flammable and limit what activities can be done in it. But I’d be surprised if they have a pure oxygen atmosphere inside a habitat that is used for multiple purpose activities for months on end like the ISS.

it seems likely that for a fair while into the future, astronauts will pre-breathe oxygen at gradually reduced pressure in the airlock the day before they do an EVA.

On Mars they might well use an equal mix of argon and nitrogen (they occur in equal quantities in the atmosphere there). With the atmosphere design it would be a case of balancing many things. The pre-breath time before an EVA, non flammability, enough oxygen to breathe, flexibility of the suit, the engineering for a habitat that has a higher internal pressure etc.

But some pre-breathe time seems likely to reduce the fire risk. The only way around it might be if they find a way to make astronaut spacesuits flexible enough to be practical with a full Earth pressure oxygen / nitrogen atmosphere inside. Perhaps they do that with mechanical exoskeletons, especially in the hands, to make movement easier, or through far more flexible suits tailored individually to an astronaut’s hands.

At any rate, with current and near future technology, the whole process of putting on a spacesuit is a matter of hours, not minutes, and it doesn’t seem likely you can just don a spacesuit like you do a wetsuit (say) any time soon.

What I just described above is an overview for the general public with some of the main steps. If you are an astronaut, there is far more to it than this. Your detailed checklist runs to hundreds of steps which they have to do in sequence, many of them timed. You can read their detailed EVA check list for the ISS here. The crew leave the crewlock on page 379 of those instructions under "Crewlock Egress". More documents for ISS EVA's here.

Surely this will get speeded up somewhat as the technology improves, but suiting up seems bound to be a slow procedure for a long time into the future, and it is one you won't want to rush.

You wouldn't want to skip on the airlock checks or suit checks for instance, as a mistake there could mean you die, or that your emergency gear doesn't work if you get into trouble. You need to be able to get into an IVA suit rapidly in an emergency. But an EVA suit is another matter altogether, it’s so complex, you’d better be sure it is working okay, and check everything, before you entrust your life to it.

This is an additional benefit for a telerobotic mission. They can just walk over straight to their workstation breathing the same nitrogen / oxygen mix they use all the time, for safety reasons. There is no need ever to depressurize and use pure oxygen, except for an EVA to repair their own spacecraft or to visit Phobos or Deimos.

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You have to factor all those details about how often you can do EVAs, how much preparation is required, etc, when you make a comparison between exploring Mars from orbit or from the ground.

I have not seen any attempt at a comparison study for exploring Mars on the surface with exploring it from orbit, except for the HERRO comparison

Technology has moved on a lot since then - but mainly in the direction of greatly improving telerobotic capabilities. The basic restrictions for spacesuits are still there, spacesuits still take ages to put on, and need extensive checking before EVA, it’s still likely that astronauts will need to have an oxygen / nitrogen mix for safety reasons etc etc.

So, I expect that a modern study will come to the same conclusion and indeed increase the advantage of the astronauts in orbit.

If anyone reading this knows of a modern comparison study do say!

For more on this see my last article under:

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As I said in the last article, none of this needs to slow down human exploration.

We have so much to do on the Moon, and, I used this in the last article but it bears repeating, the retired Canadian astronaut Chris Hadfield, former commander of the ISS, interviewed by New Scientist, put it like this in their article "We should live on the moon before a trip to Mars"

"I think ultimately we’ll be living on the moon for a generation before we get to Mars. If the world and the moon were threatened and the only way to preserve our species was to launch from Earth, we could go to Mars with yesterday’s technology, but we would probably kill just about everybody on the way."

"It’s as if you and I were in Paris, paddling around in the Seine in little canoes saying, 'We’ve got boats, we’ve got paddles, let’s go to Australia!' Australia? We can barely cross the English Channel. We’re sort of in that boat in space exploration right now. A journey to Mars is conceivable but it’s still a lot further away than most people think."

The Apollo astronauts made their voyages to the Moon seem easy, almost routine. But they were test pilots who “saved the day” several times during the Apollo program with quick witted decisions made in seconds preventing incidents that would have killed them all if their reactions had been a bit slower.

On a voyage to Mars, if an accident happens even just hours after you leave Earth capture orbit, you have over a year of travel ahead of you before you can get back again. If we had the equivalent of an Apollo 13 issue on the way to Mars no amount of improvisation could save the crew. Remember with Apollo 13 the main risk was life support, they risked running out of the capability to scrub carbon dioxide. If it weren’t for their MacGyver style antics with duct tape, then they would have died - paradoxically, with plenty of oxygen to breathe. Oxygen wasn’t the issue but just because they could no longer scrub the CO2 they risked death.

They would definitely die in an incident like that on a mission to Mars, swinging back to Earth over a year later rather than a few days later.

The Apollo 13 oxygen tank explosion happened two days into their mission. They swung past the Moon and returned to Earth in a little under 4 days. If something like this happened to an outward bound Mars mission, it would be well over a year before they could swing past Mars and return to Earth. Apollo 13 timeline

There have been many incidents with the ISS life support that were non events because replacements can be sent up within weeks, the crew can return to Earth in a fully provisioned Soyuz at any time and be back in hours. But some of them would have lead to everyone dying if they happened on the way to Mars or in Mars orbit or even on the way back until they were nearly home.

The secret to Apollo was to do one risky step at a time. It was risky, but managed risks. The astronauts were never reckless. If there was a precaution they could take, if there was a way to reduce the risk, something they could test beforehand, they did it.

We need a similar approach to Mars. If we do it like that, then humans in orbit around Mars, at a later stage, once life support is proven for the Moon, is a necessary stage anyway. We don’t want to go all out and land them on the surface too. Far more risky than “landing” in the upper Venus atmosphere or on the Moon. There is no more dangerous landing anywhere in the inner solar system inside of Jupiter.

It is so very risky because you can’t parachute to a landing on Mars unless your parachutes are ginormous. So - if you have a parachute, that is just one step - at some point you have to release the parachute, cut the lines, and start a rocket motor, or use air bags, or some way or another deal with the unsurvivable hard impact of a parachute landing.

Elon Musk proposes supersonic retropropulsion. But that is hair-raising too. Especially since they plan to do it so close to the surface that the southern uplands are out of range and if you want to land in the Valles Marineres you need to skim down actually between the two walls of the chasm in order to slow down enough in the thicker atmosphere, before finally dipping up and then down to a vertical propulsive landing on legs on the Martian surface. It is no wonder he calls it “fun but dangerous”. There is almost no chance of human interaction to save a tricky situation because sequences have to be triggered with seconds precision and the whole thing is over in minutes. And it is totally committing, once you are in the atmosphere, the only way to return is to refuel from the surface, because you lose all your speed rapidly through drag. It is not like Apollo where if they didn’t like the landing site, Neil Armstrong could have aborted back to orbit (as he nearly did, finding a good site only with seconds of fuel to spare).

I’m not saying we can never do this. But it is too much to do at once to have our first missions out to Mars orbit and first human landing all in one go, or even on successive missions.

We need the equivalent of Apollo 8 (first fly around the Moon), and 10 (did everything except land on the Moon) first before we consider the Martian equivalent of Apollo 11.

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I do not think that ten years exploring Mars from orbit as well as its two moons and telepresence on the surface will be seen as onerous by the astronauts. Especially when they also understand why they are doing it - because of the possibility that materials returned from Mars could harm the environment of Earth, and because of the possibility of native Martian life going extinct before they have a chance to study it.

And there is much they can explore in orbit around Mars, as well as the planet, its two moons, Phobos and Deimos. And actually Phobos may contribute to our understanding of early Mars. It is thought to have many meteorites in its regolith that got there within hours or minutes of leaving the surface of early Mars.

A sample-return mission to Phobos would return material both from Phobos and from Mars. Credit: NASA

Of course, meteorites that hit Mars billions of years ago sent ejecta to Earth as well, of course - but those ancient Martian meteorites on Earth must have eroded away long ago - and would be hard to distinguish from other rocks here. They are amongst the most interesting targets to look for on Earth's Moon - but also - what about Mars' closest moon, Phobos?

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Ancient Martian ejecta on Phobos should still be there, intact, preserved for billions of years. There is no process to destroy it. It can only get hidden by the accumulation of later material on the surface. It would also be uncontaminated by Earth life.

As it turns out, rather a lot of the Martian surface material can end up on Phobos after a meteorite impact.

Shows trajectories of debris from an impact on Mars and the orbits of Mars's two moon's, Phobos (innermost moon) and Deimos

As reported by Purdue university in 2012, Evidence of life on Mars could come from Martian moon, there could be significant amounts of material less than ten million years old, young enough to still have recognizable organics. About a tenth of a milligram in a 200 gram sample.

"The team concluded that a 200-gram sample scooped from the surface of Phobos could contain, on average, about one-tenth of a milligram of Mars surface material launched in the past 10 million years and 50 billion individual particles from Mars. The same sample could contain as much as 50 milligrams of Mars surface material from the past 3.5 billion years.

"The time frames are important because it is thought that after 10 million years of exposure to the high levels of radiation on Phobos, any biologically active material would be destroyed," Howell said. "Of course older Martian material would still be rich with information, but there would be much less concern about bringing a viable organism back to Earth and necessary quarantine measures.'"

So, what about the planetary protection issues? So long as Mars hasn’t sent any material up there since the most recent time a Martian meteorite left Mars for Earth, which as far as we know, was 600,000 years ago then anything there should be totally sterile. Perhaps there were more recent impacts that only got as far as Phobos but not to Earth? However, if it arrived there even as recently as 134,000 years ago, it is likely to be sterile down to a depth of one meter (that’s deep enough for a millionfold reduction of viability of radiodurans, see table 1 of this paper).

It would do no harm to check it out first. But with those figures, the chance of a planetary protection issue for Phobos seems remote even if drilling to a depth of a couple of meters, and very remote for a sample collected from its surface. There are plans to return a sample from Phobos. Russia especially has been interested in this for some time, with its failed Fobos Grunt mission. ESA has joined forces with a proposal Phootprint for a sample return, launching in 2024. It is normally classified as unrestricted category V, for planetary protection, of no concern for sample returns.

Being able to study Phobos directly is an additional bonus for astronauts in orbit around Mars.

See also

in my Touch Mars? online book, also in the same book:

For more details of some of the points mentioned here, see also the contents lists of my previous articles

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Since this is not a rubber stamping exercise, it means there is a possibility that we decide, based on what we find there, that the surface of Mars should be a no-go area for humans, in the near term for

  • a few years (time enough to study native Martian life, perhaps and learn to cultivate it in laboratories and find ways to preserve some of it in situ)
  • or decades,
  • or even indefinitely.

Though the last two cases especially would be disappointing for Mars colonization enthusiasts, it has a lot that is positive about it too, because of the implications, what we may have discovered on Mars to make such a decision. And surely they will be glad we did do the telerobotic survey in those cases!

If we do find life on Mars that is hazardous to Earth, or that is vulnerable to Earth life, both of those are very exciting possibilities. It is likely to be rather novel or interestingly different from Earth life. It can be something to look forward to.

Or it could be pre-biotic chemistry where we can see the processes that lead to evolution of life happening before our very eyes. Cells that are almost alive, but not quite, almost replicating but not quite. Not using DNA, or proteins, maybe not even RNA.

It would be the biggest discovery in biology probably since the discovery of the helical structure of DNA. It would have numerous applications too surely.

It could lead to new products useful in technology. Extremophile enzymes are the basis for a billion dollar industry. What would the applications be for a completely novel biochemistry, or life from Mars with capabilities no Earth life has ever evolved?

The increased understanding of biology may well lead to applications in medicine, agriculture, nanotechnology. As for biological processes, it would be like adding an extra dimension to our understanding of how it works. Also insights into life elsewhere in the galaxy and exoplanets and how to look for biosignatures around other stars.

And - it does not prevent us from exploiting Mars. We can do exports from Mars via telerobotics. Indeed if there is native life there, it may produce valuable products we wish to export. We can mine Mars from orbit.

We can even grow Earth plants there, from sterilized seeds, in sterile aquaponics or aeroponics. Though that may need some thought about the possibility of lateral transfer between plants and microbes, via GTA’s if it is a related form of life. Such transfer is rare, much more common from microbe to microbe, but genetic transfer from bacteria to plants has played an important role in plant evolution. If the Martian life is unrelated to Earth life, we might be able to show that gene transfer is impossible, and that it is fine to grow Earth plants on Mars from sterilized seeds.

Meanwhile the interest in Mars would lead to a growing settlement in orbit, and on its moons, and developing our interplanetary transport capabilities for more distant voyages throughout the solar system.

Then, closer at home, the Moon actually has a lot going for it, the vacuum for instance is a great advantage if you want to set up a computer chip factory - far better than anything we have on Earth except at enormous expense. If you look at the Moon in its own right, rather than as a copy of the Moon, it has one advantage after another that might surprise you. There is plenty of interest there for a vigorous program of settlement and maybe colonization in the near term without needing to look further afield, and much of the technology developed for Mars is dual purpose and would also work on the Moon such as suit ports, pressurized rovers, etc.

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There are some areas we may never send humans or not in the near future. Such as the Venus surface, with its oven heat, crushing high pressure, and concentrated sulfuric acid. Or Io within the deadly ionizing radiation of Jupiter, we couldn’t survive for minutes to hours without vast amounts of shielding.

Or diving into the visible surface of the Sun - that’s likely to be a destination for creatures like us only with seriously advanced technology.

Well, there is no guarantee that Mars will be safe for humans, and it could be a similar no-go area. We just don’t know yet.

If it has microbes that form biofilms inside our lungs, antibiotic resistant and our bodies have no defences, then, it is likely to be a no-go area for the foreseeable future. There is simply no way at present to guarantee for sure that this is not the case. Because we don’t get to write the script for this adventure and we need to be prepared to be surprised, perhaps by something nobody has even though of yet, as is often nature’s way.

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Meanwhile there are numerous places we can go in our solar system with no planetary protection problems at all, guaranteed, because we already know enough to say this.

The Moon, including ice at its poles that may be readily accessible, and may preserve Martian meteorites at cryogenic temperatures back to the early solar system (also potentially from Earth, Ceres, perhaps even Venus) - and possibly vast lunar caves. In the Jupiter system, there’s Callisto (lower radiation levels than Mars, ice and organics), Mercury, nearly all the NEA's.

Further afield, Titan, though it may have life is not a place that Earth life is able to inhabit (unless it has cryovolcanoes unlikely) and is unlikely to have life that can survive on Earth. If all that is confirmed, it is a natural place for a human base in the Saturn system and has more going for it as a place for humans than you might think, once we have the ability to get there easily. The cold is much easier to deal with than you’d expect, it has abundant energy available as wind and hydropower, a base for the entire Saturn system, and though it may seem to be gloomy - it’s the easiest place to build vast kilometer scale habitats and city domes lit up with brilliant light by the abundant wind power. You may be surprised once you think through it some more. See my

The asteroid belt is the big one that many space colonization advocates are interested- I’ve saved the best to last. Material for slowly spinning habitats with a thousand times the land area of Mars. We have a thousand potential planets out there, just in the asteroid belt, not needing terraforming over thousands of years, can be customized to any habitat we like, a few square kilometers at a time, within a decade. For more on that, see my

You can read my Touch Mars? book free online here:

Touch Mars? Europa? Enceladus? Or a tale of Missteps? (equivalent to 1938 printed pages in a single web page, takes a while to load).

You can also buy it on Amazon kindle.

My other books, which cover human exploration as well as planetary protection, and explore the case for going to the Moon first (for humans), are:

My books are all designed for reading on a computer with links to click to go to the sources, and I have no plans to attempt printed versions of them.

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