This is an article by the space engineer and Mars colonization enthusiast Robert Zubrin, The Planetary Protection Racket claiming that we don’t need to protect Earth from Mars microbes or Mars from Earth microbes. This is not the first time he has said controversial things like this, and they are not taken seriously by the planetary protection experts. Let’s go back to summer 2000, when he put forward similarly forceful arguments in print that there is no need to protect Earth from Mars microbes

This is what he wrote back then:

Robert Zubrin: "Of all the dragons infesting the maps of would-be Mars explorers, one stands out as not only illusory but hallucinatory. This is the "Threat of Back Contamination.""

"The story goes like this: no Earth organism has ever been exposed to Martian organisms, and therefore we would have no resistance to diseases caused by Martian pathogens. Until we can be assured that Mars is free of harmful diseases, we cannot risk exposing a crew to such a peril, which could easily kill them or, if it didn't, return to Earth with the crew to destroy not only the human race but the entire terrestrial biosphere."

"The kindest thing that can be said about the above argument is that it is just plain nuts....". 

(published in the Planetary Report in July / August 2000 as "Contamination from Mars, No Threat")

Just as with this present op-ed, he argued that there is no need  to do anything to protect Earth from microbes from Mars. You can imagine the surprise of those reading this op-ed who have worked for much of their professional lives on planetary protection.

Both his original post and the astonished responses by experts in planetary protection are behind a paywall, sadly. You need to be a member of the Planetary Society to read them. However, this quote from the article by Margaret Race, a zoologist and expert on invasive species, gives you an idea of the tone of their follow up article  four months later:

Margaret Race: "When I read the opinion piece by Robert Zubrin .... I didn't know how to react. As a biologist working on planetary protection and Mars sample return at the SETI institute, I wondered how an engineer and Mars enthusiast like Zubrin could make such irresponsible and inaccurate statements.

Obviously, Zubrin is entitled to his opinion, even if it's based largely on misuse of facts
. But what about the readers of The Planetary Report? Don't they deserve more than op-ed humour?"

published in the November / December 2000 edition of the Planetary Report. as "No Threat? No Way!"

She works as senior research scientist for SETI on planetary protection. (emphasis and paragraphing mine)

The second contributor to "No Threat? No Way!" was astrobiologist John Rummel, planetary protection officer for NASA at the time (and previously, NASA senior scientist for Astrobiology). You can get the tone of his response from this quote:

John Rummel: "There are days when I ask myself, "Is it worth it?" After all, given the heightened awareness about Earth organisms newfound capabilities in extreme environments - to say nothing of the troubles that immune-compromised patients face with normally benign microbes - I figure the need for contamination controls for missions to places possibly harboring life should be obvious. So I sometimes wonder if I as Planetary Protection Officer, can really make a difference. "

"I want to thank Bob Zubrin for providing this week's job satisfaction. His opinion piece in the July/August 2000 issue The Planetary Report was so off the mark that I found renewed joy in simply contemplating an answer. "

The final contributor was biochemist and microbiologist Kenneth Nealson, who is now professor of Earth sciences and Biological sciences at USC. Before that he was director of the Center for Life Detection at NASA's Jet Propulsion Laboratory (JPL). He wrote:

Kenneth Nealson: "Doing solid science in a clean and safe way will help ensure the future of the space program. Alternatively, denigrating those who would argue for safe measures regarding the unknown is ultimately irresponsible."

The space agencies world wide continue to work to make sure we protect Earth from Mars and Mars from Earth. If we ever do return a sample from Mars then there would be numerous laws to be passed, including many domestic laws in the US alone, resolving issues of public health and safety. There would also be international treaties to navigate, during which the whole process would be looked into in an open way on the public stage, a process that would take years, and possibly decades. Nothing he says can stop all that happening, and as we'll see, it's also way above the pay-grade of the Planetary Protection office too.

However, Zubrin’s views are understandably popular amongst space colonization enthusiasts. He presents them with a simple and clear message that they would like to hear. If he was right, it would all be so easy. We wouldn’t have to take any precautions at all on Mars, no more than we have to do for the Moon. It’s no wonder that his posts are widely shared and repeated over and over, while the responses by the planetary protection experts are seldom mentioned. This gives colonization enthusiasts unrealistic hopes I think, propelling them into a realm of fantasy and science fiction where Mars is like a promised land, and everything breaks in our favour, 

Promised lands don't always work, of course. I expect you can think of some examples, not just individual expeditions but failures of an entire nation, such as the attempt of the Vikings to colonize America. Perhaps some of you may also know of the attempt by the Scottish to colonize Panama, which was so disastrous it lead much of the lowland population of Scotland to bankruptcy, and resulted in an urgent need for unification with England to save them.

Flag of the Company of Scotland Trading to Africa and the Indies. Their "Darien Scheme" an attempt to colonize Panama, lead to the death of nearly all the colonists, and it also drained Scotland of an estimated a quarter of all its liquid assets. Scotland was saved from bankruptcy by England, in exchange for unification with England, higher taxes, and an agreement to service the English national debt.

These were expeditions to places that were not only easily inhabited by humans, but indeed, already inhabited. 

Anyway, let’s go through what he says in this new op ed, paragraph by paragraph: I will emphasize the points that I’ll respond to in bold - emphasizing what I take to be his main points. I think this is an excellent opportunity to start lively debates and to get people involved in thinking through issues of planetary protection for themselves. 

So, could he be right somehow? Might his views let prospective Mars colonists just breeze through all considerations of public health and safety, if he can but present them forcefully enough? Or might the experts on planetary protection who have spent their life studying the topic have something going for their views? 

Let's take a look.

Robert Zubrin: “The request by NASA for a new "Planetary Protection Officer" salaried at $187,000 per year has provoked some hilarity, but the problem is much greater than the hiring of another useless overpaid bureaucrat. In fact, NASA's planetary protection program serves no function but to cripple the space program at a cost to the taxpayers of billions of dollars.”

“The program calls for protecting Mars and Earth from "contaminating" each other, but there is not one shred of evidence to support the notion that life of any kind, let alone pathogens of macrofauna or macroflora, or free-living microbes with superior adaptation to the terrestrial environment than native species, exists on the Martian surface.”

So, he is arguing that there is no evidence of life on Mars, never mind life that can be diseases of higher animals or plants, or life with superior adaptation to Earth's environment.

To answer this, first we need to ask why there is no evidence yet for life on Mars. The answer is simple:

  • We haven’t looked.

There hasn’t been a single mission to Mars to look for life since the two Viking landers in the 1970s. Both Viking landers went to regions of Mars which we now see as amongst the least likely to have present day life. 

We now know of many potential present day habitats. But we have not yet sent a spacecraft to investigate any of them. Our current rovers are focused on the search for past habitability of Mars, for evidence of a time when there were lakes, rivers and even great seas on the planet. They are not searching for present day life and don't have the instruments they would need to carry for such a search.

Then on his point on pathogens:

  • Microbes do not need to be pathogens to be hazardous to the environment of Earth and indeed to our own macrofauna and macroflora.

This very question was the subject of a study lead by David Warmflash of the NASA Johnson Space Center: Assessing the biohazard potential of putative martian organisms for exploration class human space missions.

So how else can they be hazardous if they are not evolved as pathogens for our plants, animals, insects, fish etc?

This study identified two main ways they can harm us. they can be:

  • Infectious, causing damage only if they multiply inside the host - either invasive throughout the host or local in their effect
  • Toxic - hazardous components of the cells, or the products of their metabolism may harm other organisms incidentally - not targeted at us but still can kill us.

Amongst many examples of each of these they mention:

  • Tetanus - toxic
  • Botulism - toxic- (fatal in 5–10% of cases)
  • Legionnaires disease - infectious, colonizes our lungs. Amongst other locations it can survive in biofilms on Earth - a similar organism could survive in a biofilm on Mars or inside a single cell large organism. All it needs to survive in a human host is to be able to live naturally in an environment similar to one it would encounter in a human.
  • Clavicepts purpurea which produces ergot disease, in crops. When humans eat those diseased crops, it can lead to limb loss, convulsions and hallucination. - toxic
  • The cyanobacteria that cause algae blooms in Lake Eyrie for instance which produce a toxin that can cause sudden death in cattle or dogs within hours. - toxic

None of those are pathogens of macrofauna or macroflora, or at least, not solely such. They just happen to have products that are toxic to us. Or alternatively their native habitats sufficiently resemble the microhabitats they find in the human body to let them colonize parts of our bodies.

The cyanobacteria example is the one Chris Chyba chooses to highlight. He is professor of astrophysical sciences and international affairs at Princeton University, and has served on numerous committees and worked with the White House on national and global security issues, and directed Princeton’s Program on Science and Global Security.

He gives the example of cyanobacteria killing cattle

Lake Eyrie in October 2011 during its worst cyanobacteria bloom for a long time. The cyanobacteria produced microcystins which is a liver toxin and can cause sudden death in cattle within hours, also often kills dogs swimming in the water and is a skin irritant for people.

As Chrys Chyba summarizes the situation in his abstract:

Chris Chyba: "It is unlikely that these cyanobacteria evolved the toxins in response to dairy cows; rather the susceptibility of cattle to these toxins seems simply to be an unfortunate coincidence of a toxin working across a large evolutionary distance"

This is of no advantage at all to the cyanobacteria. Cows are neither predators on them, nor do they eat cows. Nor do they compete with each other for food, nor are they a disease of cows. It's just a coincidence that they happen to produce a chemical that is toxic over a very wide evolutionary distance.

All these examples involve a biochemistry that's the same as on Earth, as they are all Earth organisms. But what we have on Mars could be an alien biochemistry, perhaps not even based on DNA, perhaps not using proteins, or carbohydrates. We have no experience there to guide us and we have no idea what might happen. It could be harmless, unable to attack us, but it could also work the other way around, that we are defenseless against its unfamiliar biochemistry. As the Nobel prize winning molecular biologist Joshua Lederberg put it (famous for his work on microbial genetics):

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."
Finally, on his point about Mars life not adapted to Earth.
  • A microbe doesn't have to be adapted to its environment to be invasive
If you haven't checked you might be surprised to find that we actually do have invasive microbes on Earth.  These invasive microbes rarely hit the news, except for one particularly well known single cell invasive species, "rock snot" (didymo diatom) - it forms large easily visible structures like a multicellular plant, but it only needs a single cell to spread it. Diatoms are microbes that form cell walls of silica, rather unusually.

As it turns out, there are many other examples of invasive diatoms. This problem is very much under reported. Since most researchers didn't think this form of invasive species was possible until a couple of decades ago, probably there have been many invasions before then that nobody noticed. They just assumed that the problematical diatoms were native ones.

Here I'm summarizing Diatoms as non-native species, by Sarah Spaulding, Cathy Kilroy and Mark Edlund. Here are some of the more notable examples:

  • Great Lakes: over 180 non indigenous species have been introduced to the Great Lakes in the US, and of those, a study in 1999 found 24 invasive algae including 16 diatoms. Several more have been introduced since then. Most had little effect, but S. binderanus blooms made the drinking water taste bad and clogged water treatment plant filters in the 1950s-1970s. Another species A. normanii f. subsalsa formed blooms in the summer that took silica out of the water for their diatom cells which had the result that cyanobacteria out-competed other species. T. balitica from the Baltic sea had a similar effect. Some of these invaders may also have made other diatom species extinct locally.
  • French rivers: The French rivers have been studied for a long time, making it easier to track diatom introductions. Two examples of invasive species which are thought to have come from outside France recently are Eolimna comperii, Gamphoneis eriense and Encyomena triangulum. The non native species produce their largest blooms in summer. This also includes Hydrosera triquerta Wall. which blooms in estuaries and Diadesmis confervacea Kutz in the warm waters of power plant outflows.
  • New Zealand: Asterionella formosa was introduced with European settlement around 1880 and is now found in 45% of New Zealand lakes with plankton records. It probably got there on salmon eggs.

But there is one recent and very clear example, Dydimosphenia geminata

This diatom has been widespread in the northern hemisphere for at least a century. Until recently, microbiologists assumed that it was always there and had spread to those places naturally. Then it began to form large blooms in Iceland in 2000, central Europe in 2003, and the US in 2009. But though unusual, these still weren't treated as invasions because everyone assumed it was a native species to these areas already, so something to do with local conditions.

But then, it suddenly appeared in New Zealand in 2004. That was a wake up call because there was plenty of evidence to show that it was not a native New Zealand species.

It now forms large blooms in New Zealand and the government are trying to stop its spread. It may well be spread in some way by humans, and perhaps that explains the other blooms too, maybe it was a variant with new capabilities. New studies showed that its cells stay viable for weeks if kept in cool wet conditions, so it could be spread for instance on damp sports equipment from place to place even from country to country. It's remarkable for its ability to form blooms in low nutrient waters. It can have economic impacts by blocking water intakes and interfering with angling and other recreational activities.

This also helps highlight another point. An invasive microbe from Mars could be a nuisance even if it isn't devastating to the environment. For instance (my own example), life on Mars with its extremes of temperature, might be adapted to reproduce at temperatures below -20 °C, the limit for growth of Earth microbes. If it could spoil food, then our freezers would all have to operate at lower temperatures.

Or it could be better adapted in a global fashion. This is another of my own speculative suggestions and it is just to get you thinking. For instance, photosynthetic life on Earth hasn't reached anything like the theoretical peak efficiency for photosynthesis. As a striking example, this "mix in a pot chemistry" experiment added cadmium, and the amino acid cysteine (which contains sulfur) to a microbe M. thermoacetica that has a natural defense, that it covers itself in nanocrystals of cadmium sulfide, a semiconductor, to protect itself from the cadmium. Then it turns out that this natural semiconductor acts as solar cells and the microbe can use them to achieve 80% efficiency in photosynthesis, four times that of solar panels and six times that of photosynthesis. The microbe is not genetically modified. It's a wild microbe that through an accident of biology and chemistry produces super efficient miniature solar panels in the unusual environment of this laboratory experiment.They wonder if anything like this process happens naturally, perhaps with other microbes and other metals?

Mars has light levels half those on Earth, and in a dust storm 99% of the direct sunlight can be blocked out. Efficient photosynthesis would be at a premium there. It's the same for the sea bed. Brown seaweeds can't afford the luxury of rejecting light from the most energetic part of the spectrum like green plants. So, I'm not saying this is unique to Mars, but what if life on Mars has achieved a slight edge over Earth life here?

What if Mars life can achieve much more efficient photosynthesis than Earth microbes? It doesn't need to be so spectacularly good at it as those solar-cell covered microbes. It would only need to have a slight edge to eventually out compete the algae in the sea, and so remove the basis of the sea food chains. It might also stop the oceans from producing oxygen, if it uses the same method of photosynthesis as the haloarchaea, which convert sunlight directly into energy much like the cells in our retina. This would have no effect in the short term, but over thousands of years, it might make Earth uninhabitable to creatures like ourselves that need especially high levels of oxygen in the atmosphere. 

Sometimes you hear the argument that Mars life would be unable to live on Earth with its oxygen atmosphere and warmer environment. But the Mars surface with its continually changing temperatures, from temperatures so cold that dry ice forms, all the way to above 20 C, would favour polyextremophiles - versatile microbes that can handle anything you throw at them. For instance Chroococcidiopsis, one of our best candidates for a microbe able to survive on Mars, is found anywhere on Earth. It's there on cliff faces in Antarctica, in salt pillars and beneath quartz grains in the Atacama desert, through to tropical habitats in places like Sri Lanka. It's one of these polyextremophiles able to handle almost anything you throw at it, and yet it is also perfectly happy in a warm pond or a reservoir in the tropics.

What about our oxygen atmosphere though? Well, a microbe that can handle the perchlorates and hydrogen peroxides of Mars might well have no problems with our oxygen based atmosphere. Mars may have had oxygen in its atmosphere in the past too, has small amounts today, and if it has photosynthetic life, then they could also cause local increases in oxygen. After all, in experiments with lichens in Mars simulation chambers, the fungal component is kept alive by oxygen from the algae component.

In short, this is something we can't decide by thought experiments and imaginative scenarios. There's no substitute for finding out about Mars life and its capabilities first, before we can know if it is potentially harmful for Earth life or even invasive and capable of degrading our ecosystems. It could be anything from a minor nuisance that spoils food in fridges, to a global environmental disaster. Or it could be totally harmless. There is just no way to know in advance.

Many don't realize that Carl Sagan was actually an astrobiologist. As an undergraduate, he worked in the laboratory of the geneticist H. J. Muller. He then wrote a thesis on the origins of life with physical chemist Harold Urey. Joshua Lederberg was first to raise planetary protection issues back in the late 1950s, but Carl Sagan followed soon after, I think perhaps the two of them would count as the "founding fathers" of planetary protection.

As Carl Sagan said in Cosmos

Carl Sagan: “ If we wish on Earth to examine samples of Martian soil for microbes, we must, of course, not sterilize the samples beforehand. The point of the expedition is to bring them back alive. But what then? Might Martian microorganisms returned to Earth pose a public health hazard? The Martians of H. G. Wells and Orson Welles, preoccupied with the suppression of Bournemouth and Jersey City, never noticed until too late that their immunological defenses were unavailing against the microbes of Earth. Is the converse possible? This is a serious and difficult issue. 

"There may be no micromartians. If they exist, perhaps we can eat a kilogram of them with no ill effects. But we are not sure, and the stakes are high. If we wish to return unsterilized Martian samples to Earth, we must have a containment procedure that is stupefyingly reliable. There are nations that develop and stockpile bacteriological weapons. They seem to have an occasional accident, but they have not yet, so far as I know, produced global pandemics. Perhaps Martian samples can be safely returned to Earth. But I would want to be very sure before considering a returned-sample mission.

 Here is one of my "future fake news" stories. I do this to help make it more vivid. This isn't a script for a science fiction movie. It might actually happen and we might get headlines like this in the future according to some possible scenarios. This is based on Chris Chyba's example, supposing that there are algae from Mars able to survive in lakes on Earth - and at the end - well it hints on the possibility that our oceans could be taken over by algae from Mars in the worst case.

 The algae from Mars, accidentally released into our biosphere last year, have now spread to lake Eyrie. It is experiencing its worst blooms for decades. These are not just harmful to native fish. They also produce a liver toxin which can cause sudden death in cattle in hours, and also often kills dogs swimming in the water, and is a skin irritant for humans. Scientists are trying to contain the outbreak The main concern at present is that the Martian algae may be able to spread to the sea, as they are pre-adapated to salty conditions on Mars. (Future Fake News)

The photograph there is a detail from an algal bloom of Lake Eyrie in October 2011 during its worst cyanobacteria bloom for a long time. 

I made this “future fake news” story with this online Newspaper generator

Robert Zubrin: “The Viking 1 and 2 landers directly tested Martian soil, and found it free of organic material down to one part per billion accuracy.

We need to look closely at why the experiments drew a blank. And indeed, did they?

So first, yes, two of the three Viking experiments drew a blank, or at least, seemed to at the time. However, Viking found conditions similar to our harshest deserts, and even more inhospitable. The Viking instruments were very sensitive for their time, but they weren’t quite sensitive enough to detect organics in similarly harsh locations on Earth. Parts per billion sensitivity doesn't quite cut it here, especially if you detect them by heating the sample in a small oven to 200 °C, 350 °C and then 500 °C as the Viking gas chromatography / mass spectrometry experiment did.

  • Viking's ovens couldn't detect the organics at up to several million bacterial cells per gram. In tests in the Atacama desert using the same methods Viking used, they were not able to detect any life at all in these ultra low concentrations

    "Although the Viking GC/MS instruments were not specifically designed to search for the presence of living cells on Mars, our experimental results indicate that at the part per billion level, the degradation products generated from several million bacterial cells per gram of Martian soil would not have been detected." (see also original paper).

Chris McKay estimated that because of the perchlorates found on Mars, then the soil could have had an organic content as high as 0.1% and the Viking experiment would still have returned a (false) negative result.

Our later rovers such as Spirit, Opportunity and Curiosity also are not sensitive enough. They use similar ovens to anlayse the organics. We do have the capability to detect much smaller traces of organics now, with instruments far more sensitive than the ones on Viking, and also able to analyse the sample without needing to heat it to high temperatures first. There are many such instruments we could send to Mars if there was enough interest in doing it. 

However, for some reason, we just haven’t sent the necessary instruments to Mars yet. The astrobiologists have tried hard to get these experiments included. Some astrobiologists have spent years of their working life developing such instruments, for instance the team that worked on the UREY instrument for ExoMars before NASA pulled out of the collaboration with ESA. This instrument was a thousand times more sensitive than the Viking ones. The astrobiologists have got their instruments on the science payload of Mars missions a couple of times, but then they got descoped for one reason or another.

The rovers we have sent to Mars so far are not designed to search for traces of life unless it is very obvious. Their instruments are just not sensitive enough to organics for that task. What's more, the main focus of the missions were to investigate past habitability and the evidence of great flows of water, lakes and seas in early Mars. The main focus since Viking has been on instruments to analyse geology and geochemistry, with detection of organics as just one of their capabilities. Spirit, Opportunity and Curiosity would have had no chance at all of spotting the present day life that biologists have discovered in the most inhospitable areas of the Atacama desert or McMurdo dry valleys.

Then, yes, it’s true that we didn’t get proof of life on Mars from Viking. Not proof. But the final Viking experiment, Gilbert Levin's "labeled release", gave ambiguous results. Ambiguous because of the confusing chemistry. This was by far the most sensitive experiment on Viking, and indeed, the only dedicated life detection instrument ever sent to Mars. It worked by feeding the samples radioactive food and testing for radioactivity in any exhaled gases.When tested on Earth, it could detect metabolic activity of just a few cells even if they didn’t reproduce, This is the very experiment that produced the most controversial results, with its PI Gilbert Levin maintaining to this day that it may have discovered life on Mars.

There have been several attempts to explain the labeled release experiments without biology. One early idea put forward by Albert Yen of JPL was that first carbon dioxide could react with the soil to produce superoxides in the cold dry conditions with UV radiation, which could then react with the small organics of the LR experiment to produce carbon dioxide.

Perhaps the top candidate at present is the reaction studied by Quinn et all in 2013 that suggested that the perchlorates were decomposed to hypochlorite (ClO-), trapped oxygen, and chlorine dioxide. Then the release of oxygen from the trapped salts, plus the reaction of the hypochlorite with the amino acids can explain the results. There are many things to explain, particularly that two of the labeled release experiments got inactivated after storage in darkness for several months, and that the activity of the soil is significantly reduced at 50 °C. Levin and Straat in a paper published in 2016 (summarized on review the proposals. For the study with formate in the Atacama desert mentioned there see this paper. For the hyp

Also, with yet another twist on the Viking story, the perchlorates didn’t just confuse its labeled release experiments. The other experiments, the ones Zubrin cites, they were confused by them too. None of the experiments were prepared for the unexpectedly reactive Mars surface chemistry. Even if the Mars sample had millions of cells per gram, they still could have missed them.

Indeed, did the Viking landers perhaps detect those organics after all?

With this background, some others, not just Gilbert Levin, have started to wonder if perhaps he was  right after all.

Then there's the discovery by Joseph Miller of rather surprising circadian-like rhythms - like the day to night cycles of many Earth creatures, which happened in 2000. The striking thing about these rhythms in the data is that these are smoothed out. What's more, they are offset from the temperature variations by a rather large time interval of two hours. You could get ten minutes of offset from chemical processes, but Joseph Miller, who is an expert on circadian rhythms, says that two hours is hard to explain without biology.

So, I think it is fair to say that the jury is still out on this case of whether Viking detected life. I cover this possibility in my Rhythms from Martian sands - what if Viking detected life already in 1976?

Carl Sagan standing next to a model of the Viking Lander - so far the two Vikings are the only spacecraft ever sent to another planet to search for life.

Curiosity's main focus is on habitability of ancient Mars. It can search for organics, and has indeed found them, but it is not equipped to detect present day or past life itself, at least, not in the low concentrations likely in the Mars surface conditions.

To summarize

  • The Viking landers weren’t prepared for the conditions they found there, either for direct detection of life or the detection of organics. 
  • We haven’t sent any follow up experiments to check on what they found, and as a result, we don’t know for sure, to this day, whether they found life or not.

Though most scientists would say that the Viking landers probably didn’t discover life on Mars, I think it is fair to say that the jury is out on this. It seems that no amount of discussion of the old data from the 1970s can bring this debate to a conclusion. We could have settled it decades ago, and still could do, but the only way to do this is to send follow up experiments to Mars, indeed, the more we study the data, the more ambiguous and challenging it becomes.

The Viking landers in any case landed in the dry equatorial regions. There are some ideas for life there too, but they landed nowhere near any of the Recurrent Slope Lineae which we now think just possibly might provide a habitat for microbial life in that region. Nor could they travel around to inspect areas where life might be more concentrated even in the immediate vicinity of the landing site (it is often patchy in desert regions). They had no choice but to examine the "soil" directly in front of the lander itself, wherever it happened to land.

Robert Zubrin:The Martian dust is mixed on a global basis. If there is no organic material in the dust at the Viking landing sites, there is none in it anywhere.

Global Mars dust storm from 2001 Mars has local storms every two years, and from time to time it has larger global storms. The first global storm recorded is from 1873: the other ones reported were in 1909, 1924, 1956, 1971, 1973, 1975, 1977 (2 storms), 1982, and more recently in 1994, 2001 and 2007. So we get a global dust storm roughly every decade or so, though sometimes several per decade (five storms in the 1970s).

Zubrin claims that if there is any life on Mars, these dust storms will lead to easily detected levels of organics all over the surface of Mars. He concludes that since Viking didn’t detect organics at parts per billion levels in the dust at its landing site, therefore there are no organics in the dust anywhere on Mars, and so, there can't be any surface life anywhere over the entire surface of Mars.

I find it hard to know where to begin with this remark. How could he think such a thing?

There are places on Earth in remote deserts that have no organic material, for instance in some of the driest coldest part of the Atacama desert. Does that mean there is no organic material anywhere on Earth?

After all our atmosphere does a pretty good job of global mixing of dust too.

What’s more, Curiosity has found organics. There should be a lot more organics indeed, the puzzle is how little there is. Mars is closer to the asteroid belt with ten times the impact rate of Earth and gets a constant rain of organics from meteorites and comets which should have left organics present in the dust and regolith throughout the planet. If there was no degradation of the organics, Mars should have 60 ppm of organics from organics deposited into the regolith, averaged over its entire surface to a depth of a hundred meters (see page 10 of this paper). There must be some process actively removing it; probably the reactive surface chemistry.

Detail from the drilling which provided Curiosity's first detection of organics. The organics seem to come from meteorites.

The main puzzle for Mars is to understand why it has so little organics. It should have a lot more and there must be some process actively destroying it.

Also, as we saw, the Viking experiment to detect organics was confused by the same surface chemistry that confused the labeled release.

So, we have detected organics on Mars. It probably comes from meteorites or comets.

And there is no way that the mixing of the dust storms could spread organics from microhabitats into the dust in such a way that you could detect organics at high concentrations of parts per billion, equivalent to a million cells per gram, throughout the surface of Mars, when even in the microhabitats most favourable to life on Mars, it’s may well be present only at levels of millions of cells per gram. It could be even less. The most inhospitable inhabited places on Earth have cell counts ranging from a few million per cc (or gram of soil) down to 83 cells for accretion ice in Lake Vostock.

The Europa Lander report looked at analogues of the Europa ocean - but salty brines on Mars are a bit like tiny oceans, so perhaps it can give a rough idea for those too. This is from section 3 of the report. I've added some examples more relevant to Mars such as the McMurdo dry valleys and sand dunes. The numbers here all come from that report, except for the additional entries, which link to other sources. Some of them are done by direct cell count. Others use various ways to estimate the numbers of cells.

  • Cold dry desert locations such as the Atacama dry valleys - typically a few million cells per cc
  • Blood Falls outflow, Antarctica: 600,000 cells per cc.
  • Sand microbiota in migrating dunes in Qatar, 530,000 cells per cc.
  • Lake Vida ice, 444,000 cells per cc.
  • Cold icy brines: 200,000 to 200 million cells per cc.
  • 200,000 cells upper bound - site 45 for UREY testing (para 25 here). This is based on E. coli cells as the norm.
  • Circumpolar deep water around Antarctica: 74,000 cells per cc
  • Salty brines in the Mediterranean Red and Black Seas - 19,000 to 150,000 cells per cc
  • Driest parts of the Atacama desert, between 3,100 and 511,000 cells per gram of soil - with total organic content less than 0.01% (see Table 2 of this paper)
  • Driest most inhospitable part of University Valley in Antarctica - between 1,400 and 5,700 per gram of soil. Many of their samples had microbes in dormant or damaged states, needing liquid enrichment steps followed by three to five months of incubation at 5 °C before colonies appeared on the agar plates
  • Subglacial accretion ice - 120 cells per cc average (from the deepest ice core samples above lake Vostok in Antarctica - one layer of 260 cells per cc above another layer close to the lake of 80 cells per cc). From their table 3.1, the accretion ice with the higher cell density of 260 had only 60 micromoles of carbon per liter. I make that 0.000078% carbon by weight if I got the calculation right.
  • Estimate for the Europa ocean - between 0.1 and 100 cells per cc based on energy considerations. See page 3-10 of the report

Another thought here. These cell counts are for Earth life, which has a minimum size, of about 200 nm in diameter, which is actually reached for the ultramicrobacteria.

Astrobiological cells easily be smaller than Earth based cells, nanobe size, especially if it is some form of early life. To get an idea of how small they could be, we can go to the workshop held in 1999 on Size Limits of Very Small Microorganisms, in response to the discovery of what then were thought to be possible microbe fossils in ALH84001. The panel discussing cells based on alternative biochemistry came to the conclusion that an early form of life based on a single biopolymer, such as, perhaps, an RNA world cell, may be able to fit into a sphere of diameter 50 nm, or 0.05 microns.

So, if the cells were as small as only 50 nm across, that would make the volume of the cell around 0.0000005 cubic microns. By comparison, two strains of E. coli were measured with volumes of 0.6 and 0.7 cubic microns (see page 95 of this paper). You'd fit more than a million of those cells into the volume of a single E. coli cell. Even a cell count of a million RNA world cells per cc would have less by way of organics than a single E. coli cell per cc.

At any rate, whatever the actual figures for Mars, in such harsh conditions we are potentially speaking about really really tiny amounts of organics on Mars. Still, it's detectable. The instruments the astrobiologists wish to send there can now detect amino acids in concentrations as low as just one amino acid per gram. They could spot even the sparsest populations of present day life.

But many of these levels are way below the organics detection limits of Viking or any of our other instruments sent there to date, even if they were situated right there in the middle of the habitat itself.

Robert Zubrin: “The Viking landers also detected strong oxidizing agents in the Martian dust, which would destroy any microbes exposed to it. So we not only know that the Martian soil is sterile, we also know why it must be sterile.”

Yes they are strongly oxidizing agents. But it doesn’t follow at all that they would destroy all microbes exposed to them. 

After all, I am breathing oxygen, and I expect you are too. Though it’s great for us, oxygen is toxic for some other lifeforms. Indeed some biologists think that oxygen in our atmosphere may have lead to the first of our planet’s mass extinctions. For them, our atmosphere was sterilizing.

It’s rather similar for the perchlorates. They do confuse the searches on Mars because they destroy organics when heated in ovens. They also interfere with human thyroid glands. Worse still, they are probably decomposed by the harsh Martian UV into more hazardous chemicals (chlorites and hypochlorites) that can even make us unconscious, give us headaches, and cause us to have trouble breathing, or vomit.

However at the low temperatures of the Mars surface these perchlorates are much less active than they are when heated up. They are a challenge for life, but for certain microbes we have on Earth, the perchlorates even can be food. These microbes are not adapted to Mars at all. Typically they eat the perchlorates and give out oxygen as a byproduct.

With this comment, he is ignoring many years of research and a vast literature of papers describing microbes that could potentially survive in various Mars habitats if those habitats exist. Some multicellular life could survive there too potentially, such as some Earth lichens. And that's just Earth life that hasn't ever encountered Mars surface conditions, never mind evolved there for billions of years.

This of course also causes issues in the forwards direction. Earth life could potentially harm Mars life too.

Cassie Conley, NASA's planetary protection officer, put it like this:

Cassie Conley: “For certain types of Earth organisms, Mars is a gigantic dinner plate. We don’t know, but it could be that those organisms would grow much more rapidly than they would on Earth because they have this unaffected environment and everything is there for them to use.”

To give an idea, let’s do a list of some of the candidate organisms that may be able to survive on Mars according to various research papers:

  • Chroococcidiopsis - UV and radioresistant, and can form a single species ecosystem. It needs no other forms of life, and only requires CO2 , sunlight and trace elements to survive.
  • Halobacteria - UV and radioresistant, photosynthetic (using hydrogen directly - proton pumps, doesn't generate oxygen or sulfur), can form single species ecosystems, and highly salt tolerant. Some are tolerant of perchlorates and even use them as an energy source, examples include Haloferax mediterranei, Haloferax denitrificans, Haloferax gibbonsii, Haloarcula marismortui, and Haloarcula vallismortis
  • Some species of Carnobacterium extracted from permafrost layers on Earth which are able to grow in Mars simulation chambers in conditions of low atmospheric pressure, low temperature and CO2 dominated atmosphere as for Mars.
  • Geobacter metallireducens - it uses Fe(III) as the sole electron acceptor, and can use organic compounds, molecular hydrogen, or elemental sulfur as the electron donor.
  • Alkalilimnicola ehrlichii MLHE-1 (Euryarchaeota) - able to use CO in Mars simulation conditions, in salty brine with low water potentials (−19 MPa), in temperature within range for the RSL, oxygen free with nitrate, and unaffected by magnesium perchlorate and low atmospheric pressure (10 mbar). Another candidate, Hxalorubrum str. BV (Proteobacteria) could use the CO with a water potential of −39.6 MPa
  • black molds The microcolonial fungi, Cryomyces antarcticus (an extremophile fungi, one of several from Antarctic dry deserts) and Knufia perforans, adapted and recovered metabolic activity during exposure to a simulated Mars environment for 7 days using only night time humidity of the air; no chemical signs of stress.
  • black yeast Exophiala jeanselmei, also adapted and recovered metabolic activity during exposure to a simulated Mars environment for 7 days using only night time humidity of the air; no chemical signs of stress.
  • Methanogens such as Methanosarcina barkeri - only require CO2, hydrogen and trace elements. The hydrogen could come from geothermal sources, volcanic action or action of water on basalt.
  • Lichens such as Xanthoria elegans, Pleopsidium chlorophanum, and Circinaria gyrosa - some of these are able to metabolize and photosynthesize slowly in Mars simulation chambers using just the night time humidity, and have been shown to be able to survive Mars surface conditions such as the UV in Mars simulation experiments.

Zubrin: Even in the absence of the sterilizing oxidizers detected by Viking, conditions on the Martian surface are such so as to preclude active microbial metabolism. Active life cannot exist without liquid water. There is no liquid water on the Martian surface.

What he says here would have seemed unremarkable a decade ago. It was the consensus of nearly all scientists, not all, about ten years ago, that there could be no life on Mars because there is no liquid water on Mars (they thought).

So what he says here is okay, except that he is nearly a decade out of date. Ever since the droplets of what may have been salty brine that formed on the legs of Phoenix in 2008, coalesced, then vanished (probably fell off), scientists have found more and more ways that liquid water may be possible on Mars.

Also this is not true:

“Active life cannot exist without liquid water”. - Wrong

Certain lichens and cyanobacteria are able to survive in Mars simulation conditions and actually metabolize and grow using only the night time humidity. In their cold dry natural habitats on Earth they are able to survive without any liquid water. They manage to pull off the same trick in Mars simulation chambers too.

Researchers at DLR (German equivalent of NASA) testing lichens in Mars simulation experiments. These can survive without liquid water on Earth and can manage the same trick in Mars simulation conditions using only the 100% night time humidity to metabolize and grow.

So, life could survive on Mars using just the night time humidity. But as it turns out, there's the potential for liquid water there too. There are five basic ways microbes can make use of water on Mars mentioned in the literature. 

  •  It can be salty - salty water has a higher boiling point than fresh water. By salts there we include perchlorates, sulfates, chlorates etc. For a chemist, any time you neutralize an acid with a base, it creates a salt. For instance those copper sulfate crystals you may have made in school chemistry lessons are also salts for chemists. Salts can often take water out of the atmosphere and become damp in that way when the humidity is high. On Mars also, water can form on salt / ice interfaces.
  • It can be trapped partially or totally beneath a layer of ice (this often happens in Antarctica where clear ice has a layer of pure water below the surface heated through the solid state greenhouse effect), dust, rock, or caught in pores in salt (as often happens in the Atacama desert salt pillars).
  • It can form temporarily at times of higher humidity at night, and dry out in the early morning as the morning frosts evaporate into the atmosphere, perhaps by a layer of more humid air hugging the surface
  • It can form thin layers only a few molecules thick on the surface of rocks at temperatures well below the freezing point of ice. Though such layers may seem too meager for life, actually it turns out that in very cold dry conditions on Earth, microbes can exploit it. 
  • They can take it directly from the atmosphere, as in the DLR experiments.

Microbes can also form biofilms. These could make liquid layers more habitable than they would be otherwise by changing the microclimate inside the biofilm. 

Here are some of the suggested locations for liquid water on Mars based on these principles. The links take you through to my planetary protection book Touch Mars? where you can find out more.

Robert Zubrin: “If, despite all the above, there somehow were Martian surface microbial life, then it is already here. The Earth is struck by about 1,000 pounds of Martian meteorite a year. These rocks have been ejected from three different sites during the past 10 million years or so.”

This is one of his favourite arguments, and is often repeated in online discussions as a knock down argument. However when you look at it a bit more closely, it’s not nearly as conclusive as you might think.

First, most recent rocks left Mars 600,000 years ago. Also the meteorites are very small, meaning they have little protection from cosmic radiation. The meteorites we have so far all had pre-atmospheric sizes of 23- 25 cm.

The EETA 79001 meteorite, with the youngest cosmic radiation exposure age of all our Martian meteorites. It left Mars only 600,000 years ago. It is also a very young rock. It formed on Mars only 180 million years ago.

According to impact modeling, typical meteorites will be on average 30 cm in diameter, which matches our observations rather well.

According to those studies, then the largest meteorites likely to get to Earth are 2 meters in diameter, at least for the sizes of impacts that sent material here for the last twenty million years. See page 1355 of this paper (and discussed in next section).

So there is no chance at all of us being hit in the present day by a meteorite large enough to have shielded life in the meteorite from cosmic radiation for as long as 600,000 years.

Yes Earth is hit by half a ton of Mars meteorites we receive every year - but almost certainly, all of it is thoroughly sterilized of Martian life if it ever contained any.

There is more to it than that though. Even 600,000 years ago when those first meteorites hit Earth from the most recent impact on Mars, the chance of any life getting to Earth from Mars was very low.

Those impacts are nearly all into young terrain in the southern hemisphere, because the rock needs to be quite strong for the impact shock to send some of it into space for such small impacts as the ones that happened in the last 20 million years or so.

There are many more impediments to life getting into the rocks.

  • The meteorites we have all came from at least 2 meters below the Mars surface (as we know from ionizing radiation evidence),

    Again this fits the impact modeling, which shows that shallower material can’t get into space after a medium sized impact on Mars like the ones that sent those meteorites our way.

The suggested habitats on Mars are either deep below the surface, in ice melted by geothermal heating, or in the deep hydrosphere kilometers deep, or in the top few centimeters. There is no way these can get ejected from Mars by such an impact, except in a very lucky hit on a shallow subsurface geothermal habitat. Mars is not completely inactive but any geothermal habitats must be very rare with no volcanic activity going on at all at present. Without geothermal heating, the permafrost layer is only a couple of centimeters below the surface even at the equator (except that it is also typically ice free there), so any rocks we get from Mars are form deep inside the permafrost layer on Mars.

The potential habitats on Mars are also generally in dust, sand, salt, and ice. They are fragile habitats that might well not get into orbit even after a large impact.

Also the shock of ejection from Mars is sterilizing for most microbes - some could survive it, but most will not.

Finally, the meteorites, if of any size, large enough to protect microbes from cosmic radiation, get their outermost shell ablated as they enter the Earth’s atmosphere. This would sterilize any life that is on the outside of the rock, for instance, typical photosynthetic life.

Robert Zubrin: “A conservative linear extrapolation backwards (conservative because impact rates were higher in the past) over the past 3.6 billion years then indicates that the terrestrial biosphere has already received some 3.6 trillion pounds of samples from Mars coming from over a thousand different sites scattered across the planet. Examination of samples of this material show that perhaps 10 percent of it is ejected unshocked, which means bacteria could survive the ejection event.”

I’m not sure what his source is there. It’s lightly shocked, but lightly shocked in this sense means - not the extreme levels of shock originally thought in the early modeling.

Techy detail: the range of shock experienced by the Martian meteorites we have, when they left Mars, was 5 - 50 GPa (billion Pascals). Chroococcidiopsis can survive up to 10 GPa. The microbe Bacillus subtilis and the lichen Xanthoria elegans survived up to 45 GPa. See this paper.

Robert Zubrin: “There is also little doubt sizable fractions of the ejected putative bacteria could survive the interplanetary transfer and re-entry at Earth as well.”

Not if they can’t get into it in the first place, or if they get killed due to the shock of ejection.

Also it seems he hasn’t taken account of the research into atmospheric re-entry into Earth’s atmosphere, which ablates the surface and probably rules out transfer of photosynthetic life from Mars to Earth.

See Charles Cockell’s study which I discuss here:

Charles Cockell's experiment - the circle shows where they attached a sample of gneiss with chroococcidiopsis below the surface at a depth where it could still photosynthesize in natural conditions. None of it survived re-entry, not even biomolecules.

Robert Zubrin: “In light of this, planetary protectors need to explain why building a Maginot Line around NASA's 1 pound sample is a worthwhile activity while Mother Nature, laughing at their quarantine orders, continues to deliver thousands of pounds of uninspected and unsterilized materials to Earth.”

His meteorite argument here is a good one generally. It works for comet and asteroid sample return. It’s the “Natural contamination principle”. It’s very useful there. We’ve had several comet and asteroid returns now, and those returns would have been very hard to do indeed if it weren’t for the natural contamination argument.

If we could prove that exchange of samples via meteorites transfers the same microbes as easily as our sample returns do, we could use this argument.

Sadly though, we can’t, for Mars. The upside is that this biological natural barrier makes it more likely that Mars is biologically interesting.

The transfer was easier

  • When Mars had oceans and lakes
  • If these oceans and lakes had abundant life
  • During the very largest impacts at the time of the "late heavy bombardment" around 4 billion years ago.

Artist's impression of the Moon during the Late Heavy Bombardment (top) and as it is now (bottom) by Tim Wetherell of the Australian National University

This may well have been the most likely time for life to be transferred from Mars to Earth. This was between 3.8 and 4.1 billion years ago when there was a late surge of impacts by large debris that still remained within the solar system before it settled down to its present state.

Then there’s another point here too.

How do we know that life transferred from Mars to Earth hasn’t caused extinctions in the past? There are many unexplained past extinctions. It would be very hard to prove conclusively that none of those major or minor mass extinctions were caused by life that got to Earth from Mars, in a meteorite.

Indeed, if photosynthetic life did come from Mars, if it could transfer here that easily, then maybe the first oxygen producing photosynthetic life on our planet evolved first on Mars, which was habitable before Earth, with early warm oceans. If so, well that would mean it caused the earliest known possible mass extinction on Earth, the great oxygenation event.

After all, if Earth and Mars life are closely related, then invasive microbes from Mars can blend in with the other microbes already on Earth. If you find an invasive microbe here, how then can you tell if they come from Mars, or evolved here?

The National Research Council looked into this question in their "Assessment of Planetary Protection Requirements for a Mars Sample Return". They don't go into their reasoning in any detail, and they didn’t publish it as a response to Zubrin, but they say that they were unable to rule out the possibility that life from Mars could have caused mass extinctions on Earth in the past. They put it like this (page 48):

NRC: "Despite suggestions to the contrary, it is simply not possible, on the basis of current knowledge, to determine whether viable martian life forms have already been delivered to Earth. Certainly in the modern era, there is no evidence for large-scale or other negative effects that are attributable to the frequent deliveries to Earth of essentially unaltered martian rocks. However the possibility that such effects occurred in the distant past cannot be discounted. Thus, it is not appropriate to argue that the existence of martian meteorites on Earth negates the need to treat as potentially hazardous an samples returned from Mars via robotic spacecraft. A prudent planetary protection policy must assume that a potential biological hazard exists from Mars sample return and that every precaution should be taken to ensure the complete isolation of any deliberately returned samples, until it can be determined that no hazard exists." (emphasis mine).

The argument was taken up again in a paper published by Alberto Fairén and Dirk Schulze-Makuch, in "The Over Protection of Mars"., published in Nature Geoscience in June 2013. Many humans to Mars enthusiasts will have heard of this paper, which is popular amongst them of course, because of its message that we don't need to take any precautions. This is an example of our natural "Confirmation bias":

"a tendency to search for, interpret, favor, and recall information in a way that confirms one's preexisting beliefs or hypotheses."

Its rebuttal is so seldom shared, that hardly anyone knows about it. This is the article "Appropriate Protection of Mars", published in Nature Geoscience just one month later, in July 2013, by the current and previous planetary protection officers Catherine Conley and John Rummel. The two papers are summarized in The Overprotection of Mars? published in NASA's online astrobiology magazine, and also in Overprotection may be hampering hunt for Mars life in New Scientist.

Robert Zubrin: “The argument is not whether measures should be taken to protect the Mars sample from terrestrial contamination. Everyone agrees that such measures should be taken to preserve the scientific value of the sample. The issue is whether foundationless fears should be allowed to distort the mission so as to increase the chance of failure. NASA lost two Ranger lunar missions due to completely pointless spacecraft sterilization measures demanded by the planetary protection folks.

That was with the technology of the early 1960s!

Ranger 5 which was launched in 1962. This mission was sterilized with dry heat and terminal-gas sterilization. It missed the Moon through loss of power and didn’t send back any images. Some of the scientists thought this might have been because of the sterilization procedures. After protests, the Working group on Biology in July 1962 revisited the situation and came to the conclusion that “contamination of the Moon does not constitute as serious a problem as is the case of the planets.” After that planetary protection measures were less stringent for the Moon.

There is no proof that it was lost due to the sterilization procedures. And in any case that was with early 1960s technology. For details see page 50 of When Biospheres Collide.

Planetary protection measures since then haven’t caused any mission failures and it’s an arguable case whether or not those early primitive landers were harmed by the heat sterilization methods they used back then. They might have malfunctioned anyway.

Also, at the time it was a possibility that the Moon had subsurface habitats for microbes, which could be infected. It’s only with hindsight that we now know that there was no need to sterilize them.

NASA changed their objective after the failures of Rangers 1–5 and this review. After that their objective was to protect the Moon against “widespread or excessive contamination”

Their reasoning is explained on page 50 of When Biospheres Collide.:

“NASA based its policy on prevailing scientific opinion that the Moon’s harsh surface environment would make reproduction of Earth microorganisms extremely unlikely, and that if viable Earth organisms were able to penetrate to the lunar subsurface and survive, any propagation would remain exceedingly localized”

However they

“did not lift sterilization requirements for planetary missions as it had done for lunar exploration. The planets were considered potentially contaminatable. The manual stated that NASA policy was to prevent planetary biological contamination “until sufficient information has been obtained . . . to ensure that biological studies will not be jeopardized.”″

Robert Zubrin: Now, as a result of their demands, in 1998 Jet Propulsion Lab adopted a mission protocol for the Mars Sample Return stating that if signal confirming sample confinement was lost from a returning sample craft, the return vehicle would be directed to bypass the Earth.

That’s a bit out of date, citing a 1998 mission protocol.

We don’t know how the 2030s sample return will be done, if it is at all. It is not yet even a mission proposal. It is a decision for the next decade, the 2020s, whether to attempt it. It will be sure to compete with other proposed flagship missions for that decade.

Robert Zubrin: “Think about that. We have already spent three decades planning a Mars Sample Return mission, and it is likely we'll spend at least another. Before it's done, several billion dollars will be spent in an effort to get a sample from Mars. The planetary protection office has greatly increased the cost and risk, and delayed the schedule of the Mars Sample Return, by requiring that it be done with multiple spacecraft and in-space rendezvous in order the "break the chain of contact with Mars."”

Of course that makes sense if you believe with Zubrin that there is no risk to Earth.

But if you don’t have his confidence in the harmlessness of a Mars sample for Earth, the situation is as Margaret Race put it:

Margaret Race: "He's confident in our impressive technological prowess; he's raring to go and doesn't want anything to slow down or stop our exploration of Mars - especially not burdensome regulations based on very small risks and scientific uncertainty. Yet when he suggests that there's no need for back contamination controls on Mars sample return missions, he's advocating an irresponsible way to cut corners. If he were an architect, would he suggest designing buildings without smoke detectors or fire extinguishers?"

Anyway there are other solutions for a Mars sample return. One possibility is to sterilize it before return to Earth. Another is to just not do the sample return at all.

Actually, it’s not the astrobiologists or the planetary protection office arguing for the sample return. What they say is only: “if you do it, you’d better do it in a way that is safe for Earth”.

There are many options here. We can do a far less expensive sample return with a sterilized sample, or continue to study in situ.

If you do some research to find out what the astrobiologists themselves say, you find many papers by different groups of astrobiologists, all arguing strongly against a sample return. These include a white paper submitted to the decadal review itself.

They say clearly that in their professional opinion, this mission is not likely to answer key questions in their discipline. They say that it is likely to return a sample as ambiguous as the Mars meteorites we have already.

Here is another of my "future fake news" stories to dramatize the idea:

The image here is a detail of one of the less well known close up electron microscope photographs of ALH84001, the controversial meteorite that was first announced as the potentially the first discovery of life on Mars, but later the announcement was withdrawn as premature. 

It remains controversial to this day, with astrobiologists arguing both sides of the case.

Even the book “Safe on Mars” from 2002, cited by the decadal review, though now 15 years out of date, already says that an in situ search would be better than a sample return, if we have the technology. They say:

"As stated above, there are currently no measurement techniques or capabilities available for such in situ testing. If such capabilities were to become available, one advantage is that the experiment would not be limited by the small amount of material that a Mars sample return mission would provide. What is more, with the use of rovers, an in situ experiment could be conducted over a wide range of locations."
(Page 41 of Safe on Mars) (emphasis mine)

So, actually, when you read it in detail, it's a similar recommendation to the one by the astrobiologists. With in situ searches you are not limited to such a small sample, and can explore a wide range of locations.

Well, now, these capabilities are available. "Safe on Mars" was written just two years after completion of the first draft of the human genome, the three billion dollar human genome project that finished in in 2000. At the time it would have seemed almost inconceivable that we could send a gene sequencer to Mars, as this is how they did the sequencing, with many work stations simultaneously and a lot of human interaction:

We now have that technology for in situ searches that they talk about in that report. That makes an in situ study the best way to find out about life on Mars. All the writings by astrobiologists that I’ve seen agree.

Some of the equipment used to sequence the human genome for the first time as part of a three billion dollar project, first incomplete draft released in 2000.

This is what a DNA sequencer looked like around the time of the publication of “Safe on Mars”. A whole room full of complex equipment.

Now Oxford Nanopore markets the MinION, a gene sequencer on a USB stick, which can do the same thing!

Image from Smithonian magazine announcement of the minION before it was in production. Now it is widely used.

This is what a DNA sequencer looks like today.

The advance in technology in the last 16 years in this field has been just incredible. This commercial miniaturized gene sequencer, combined with a commercial miniature nucleic acid extraction device is the basis for SETG - a gene sequencer to send to Mars. They have all the components in place, but with some steps still done manually. It combines together two commercial devices - the minION just mentioned, for DNA sequencing, along with SimplePrep X1 for DNA extraction.

The miniaturized commercial gene sequencer minION A, with the DNA extraction device SimplePrep X1 form the heart of SETG which astrobiologists hope can be sent to Mars to do DNA sequencing on the planet. See figure 3 of this paper. It's currently at technological readiness level 4 (some steps still have to be done manually).

The final instrument will have the whole process automated, end to end, in a miniature device you can hold in your hand, from sample acquisition all the way through to DNA sequencing. It's at technological readiness level 4 (some steps still have to be done manually), moving towards levels 5 and 6 (final stage before testing in space conditions). Techy details here. Such a device would be inconceivable with the technology of the year 2000.

It's the same with many other instruments that were huge laboratory filling machines back in 2002. They have already been miniaturized and a fair number also tested in space simulation conditions, and could easily be sent to Mars.

The instruments we could send to Mars now include electron microscopes, and ultra sensitive biosignature detectors able to detect a single amino acid in a sample. Our instruments also include the exquisitely sensitive electrophoresis "lab on a chip" methods mentioned by Bada et al. Another new idea is the Solid3 approach of using polyclonal antibodies - which can detect, not just the organics you find in animal bodies, but a wide range of organics, again with exquisite sensitivity, in a "lab on a chip". See In situ instrument capabilities in my book on planetary protection Touch Mars?

I think it is pretty much certain that a modern report on “Safe on Mars”, with the technology we have fifteen years after its publication, would recommend in situ studies over a sample return to find out if Mars is safe for humans.

There only reason now to do such an expensive sample return is for geological reasons, and as a technology demo. We still can’t miniaturize a particle accelerator and though we can do isotope studies on Mars, and already do, a particle accelerator will permit more sensitive studies of more isotopes. Geologists would love to have samples for that reason alone.

The sample would be of some interest to the astrobiologists, but not at the cost of millions of dollars per gram. That’s especially so because we already have Mars meteorites here already at a fraction of that cost.

It could be useful a technology demo for a future astrobiological sample return. but if so, why not sterilize it? On the remote chance it did have extant life in it, we’d still be able to tell from the sterilized sample and that would give great incentive to go back and study it in situ and return it to the vicinity of Earth in conditions that keep it alive (the journey back might well kill it) and in a way that protects Earth.

If we want to have the ability to study unsterilized portions of the samples - we can do that too. Return the original sample to above GEO, and return half of the sample sterilized to Earth, leave the rest in orbit in case it is of interest to study in its unsterilized state.

Then - if the unsterilized sample turns out to be of astrobiological interest after all - we then take the necessary precautions, with more knowledge of what is in it by then. If it does have some novel form of biochemistry, something never seen on Earth before, or anything as hard to predict as that, we might well decide to just study it in orbit via telerobotics. In any case that would be an extended mission and we could develop its protocols as needed. The sample, above GEO would be easy to send robots to from Earth.

Robert Zubrin: “If not for them, using the 2,200-pound landing capability demonstrated on the Curiosity mission, we could land a fully-fueled two-stage Mars Ascent Vehicle with a Spirit-sized rover, capable of gathering samples and sending them in a capsule directly back to Earth. Such a mission could be readily accomplished with a single Atlas V launch. Instead, the agency has turned the mission into a long-term, multi-launch, multi-spacecraft vision to satisfy its charlatans.

The Curiosity 2020 mission and its successor (if there is one) is not based on any suggestion by the Planetary Protection Office or by astrobiologists.

It seems mainly motivated by planetary scientists, especially planetary geologists, and the space colonists also. I haven’t found evidence of a single astrobiologist campaigning for it.

The only astrobiologist to suggest a sample return at all, in my literature search, is Chris McKay and his proposal is - just grab a sample of dirt as a technology demo, and return it - one day on the surface, no rover

This is much like Zubrin’s own proposal but even simpler. There’s also the idea of SCIM to skim the atmosphere during a Mars dust storm and return a sample of high altitude dust.

Animation for Chris McKay’s - just grab a sample of dirt as a technology demo, and return it

All that complication Zubrin mentions is due to planetary scientists, and especially, planetary geologists, attempting to achieve the “perfect sample return mission” on the basis of the idea it is their one chance, “betting the ranch” on this mission.

Astrobiologists think that this expensive approach is nuts, to use one of Zubrin’s favourite expressions, at least for their discipline. They say we just don’t know enough yet to intelligently select samples to return from Mars.

That’s especially so since there’s a constant “rain” of organics from comets and meteorites so unless you can detect life “in situ” in a robust way, you are far more likely to return a bunch of organics from meteorites than anything associated with extant or extinct life on Mars.

There are many interesting sample return missions we could do at a far lower cost.

The other main idea for a sample return from Mars, often mentioned, and even attempted by the Russians is a sample return from Phobos. This could tell us a lot about the Martian past because of the meteorite debris from Mars on Phobos. It could give us samples from not just present day Mars but from the distant past right back to the early days of our solar system, unaltered geologically since they landed on Phobos. Like our Mars meteorites, but ones that were ejected from Mars not just in the last twenty million years, but billions of years ago, even back when it had oceans on its surface.

But whatever we do, we still need the equivalent of smoke alarms, to protect Earth, if the expert astrobiologists who assess these things think they are needed.

We need to evaluate this need for precautions based on what could be there. Not on what we know to be there. You don’t wait until you have evidence of a fire starting in your house before you install a smoke alarm.

As Martin Rees put it when talking about intelligent ETIs,

“absence of evidence is not evidence of absence.”

At least, it isn’t if you haven’t looked yet.

Robert Zubrin:Having inflicted such extraordinary costs, the back contamination worthies still argue all that time, effort, money, talent, and potential for discovery of the mission should be tossed like garbage into interplanetary space to appease tabloid fears over a non-existent menace.”

“If some crank were to destroy the Mona Lisa out of fear that witchcraft might be associated with the painting, most people would consider his action a crime against art. Now we have space agency officials preparing similar irrational vandalism against the Mars Sample Return. Perhaps it is time that NASA rethought its "planetary protection" program. Continuing to lend credence to the irrational could be very costly indeed.

This again of course depends on his previous arguments. If you agree with him that the sample would be harmless to us, what he says there makes sense.

But if the sample could potentially harm Earth’s biosphere, even if the risk is low probability, many would say that we simply shouldn’t take that risk. The potential gain in scientific knowledge is just not worth taking a tiny risk of degrading our biosphere permanently for all future time

The best solution I think myself, for the first sample return, is to say “this is a technology demo, just sterilize it”. Then you don’t need to build a Mars receiving facility.

There are also the vast numbers of laws we’d have to pass. Here is a summary of Margaret Race's findings:

“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.”

When you bear in mind that even relatively simple legal cases at this level can take a decade, and the complexity of all the laws that would need to be passed, and the international nature of some of the deliberations, probably NASA should have started on the legal processes already if they want to be legally cleared for a sample return in the 2030s. That's assuming there are no serious objections to the plan. She remarks that there have often been legal challenges that last for long periods of time for the Environmental Impact Statements.

Also, she says that the courts would not tolerate shortcuts. NASA would not be the only agency involved in these legal decisions.

Quarantine regulations are likely to be particularly tricky, as they could lead to incarceration of government employees and other people (in the case where they are contaminated by the sample accidentally or for some other reason). Commenting on this, she says

"Quarantine regulations are thus intimately linked with constitutional questions about deprivation of liberty and property over which NASA has questionable authority. Clearly before a sample return mission can be mounted, significant clarification will be needed on many scientific, operational and legal questions related to quarantine and exposure concerns, in order to minimize the opportunity for challenges and at the same time ensure public security"

All this complexity is nothing to do with the planetary protection office. It’s because we live in times with far more legislation to protect us than there were at the time of Apollo. The approach of Apollo simply would not be tolerated nowadays. Though we may grumble when the laws affect us, most of us are grateful for these laws when they protect our lives.

So, that’s my recommendation: Sterilize the sample, or at least any part that returns to Earth (if we leave the rest above GEO), and the whole thing becomes far simpler.

I think NASA and Congress will come to the same conclusion if we ever get to the point where they start work on the Mars sample return mission in detail. They would be faced with the double whammy of the sticker shock of the cost of a Mars Return Facility (half a billion dollars on last estimate) just to return 450 grams, plus the prospect of having to spend a decade, maybe more, passing all the legislation. They may well come to the same conclusion “Why not just sterilize it, or the part that we return to Earth?”

Robert Zubrin:Even worse, there can be no guarantee a human Mars mission won't crash, spreading Earth microbes all over the Martian landscape. If so, so long as the Planetary Protection office exists there can be no human missions to Mars – not by NASA, SpaceX or any other American organization.

So, first it is good to see that he acknowledges that a human occupied ship could crash on Mars, and that if it does so, it would lead to irreversible contamination of Mars with Earth microbes. Of course from his point of view that is going to cause no scientific problems, but others would disagree there.

Anyway he is addressing the wrong people there. It’s way above the paygrade of the planetary protection office. It’s based on the Outer Space Treaty, the same treaty that prevents the US, Russia, China etc from placing nuclear weapons and other weapons of mass destruction in orbiting satellites.

This requirement to protect Earth and Mars in the treaty is an international requirement. China, ESA, Roscosmos, JAXA, the Indian Space Organization - they all follow the same guidelines. Even the United Arabic Emirates , though they haven’t ratified the treaty, they also will follow the planetary protection guidelines for their proposed mission to Mars.

Most countries have ratified, all have signed, and there is no country world wide that says they wish to go against the provisions to protect Mars and Earth.

This provision is just sensible. Like smoke detectors in the reverse direction, and as for protecting Mars again, it just makes sense that you want to find the life that is there. It’s easy to detect life if you bring it yourself but it would be the worst anticlimax of all our exploration of Mars, to search for life there only to discover our own microbes, and that we have irreversibly contaminated it and can never know for sure what was there before we got there.

The planetary protection policies are decided in international committees under COSPAR, not NASA. The rules apply to all space agencies world wide. The NASA planetary protection officer is involved in making sure that NASA missions abide by the guidelines.

The actual policies themselves are “well above their paygrade” as Cassie Conley puts it when asked questions about them.

The precautions to protect Earth are also based on many other international and domestic laws. This is above the paygrade even of COSPAR.

And - yes they are there for a reason. There is no guarantee that Mars is a safe place for humans to go, either safe for Mars, or safe for Earth if anything or anyone returns from Mars to Earth unsterilized. We just don’t know.

The perchlorates in the dust, though they are food for some microbes, are certainly hazardous to humans. They would disturb the thyroid gland, interfering with uptake of iodine. More seriously, they are also likely to be decomposed by ionizing radiation into the reactive reactive chlorites (ClO2) and hypochlorites (ClO) which have more serious and immediate effects "such as respiratory difficulties, headaches, skin burns, loss of consciousness and vomiting" (quote from page 3 of this paper).

We can protect humans on Mars against the dust, by filtering it out carefully, using special spacesuits, known as suitports which you enter through the back, so that only a cubic foot of air contacts the Mars atmosphere when the airlock is opened - and it rushes out, so not much dust gets in - and the suits are left attached to the spacecraft, after the astronaut exits through the back.

This shows the “Suit Port” which can protect astronauts on Mars from the potentially harmful Mars dust, by never letting more than tiny amounts of the dust get into the habitat or suit. You enter the suit from the back as shown. Then two plates are put into position behind you forming a minute airlock of only a cubic foot of air. These then are separated leaving one plate to seal your suit and another to seal the habitat. To return to the habitat, reverse the process. The same method can protect lunar astronauts from lunar dust.

The Mars dust though could potentially have the very hazardous chlorites and hypochlorites that can cause unconsciousness, vomiting, headaches etc. The lunar dust is a known quantities and we know that humans can tolerate it short term. The Moon also doesn’t have dust storms and the dust is easily turned into glass using a microwave. This is useful for the Moon. We don’t know but it might even be essential for survival on Mars if we ever send humans there to the surface.

We can work around hazardous chemicals. However, the example of the perchlorates shows that it’s not a planet “designed” for humans to live there.

It’s also so cold at night carbon dioxide freezes out as dry ice for 100 days a year. It gets half the solar power of Earth and the dust storms block out 99% of the sunlight for weeks on end every few years. What about its microbes, if it has them?

This is not a script in a science fiction movie where the humans always win out against the odds and random chance always breaks in our favour (unless it goes the other way for dramatic tension). Nor do we have any previous experience of exploring other terrestrial planets with habitats for life on them to guide us here. There is no guarantee that we will discover that Mars biology is safe for humans.

We have to find out what the situation is and take it from there.

With that background, a sample return from a few drilled rocks in equatorial regions can’t possibly prove that Mars is safe for humans or that our microbes are safe for Mars. With such a varied planet, as we now realize, and given that life also is often patchy in desert locations, it can only really tell us something about those particular drill spots on one location on Mars.

The only way to have a reasonable understanding of safety of Mars to humans and our microbes for Mars is to have an extensive astrobiological investigation of Mars. So far we haven’t even started on that.

Meanwhile, I know Robert Zubrin is dead keen on sending humans to Mars as soon as possible. I can imagine it is frustrating, to have not seen this vision come to past after decades.

But we do have the Moon close to hand. We know already that Earth life is safe for the Moon and that the Moon samples are safe for Earth.

Then, further afield, there’s Callisto in the Jupiter system, there are the asteroids, there are the Mars moons to explore.

Why not hold off from landing humans on Mars, until we know that it is safe for humans to do that, safe for Earth, and also, that it is not going to adversely affect the science research we want to do on Mars?

Robert Zubrin: “NASA is currently spending around $10 billion per year on a human spaceflight program whose supposed objective is a human mission to Mars. At the same time, it is funding a department whose purpose requires it to prevent such a mission from ever happening.”

“That's just nuts. The Planetary Protection Office needs to be shut down.”

Well as you’ll guess from my responses, I think the Planetary Protection Office fulfills a vital need.

Also, his conclusion seems to show a confusion between the roles of the Planetary Protection Office and COSPAR. The office does not set forth any of these policies. They are the result of international consultations of many experts.

Shutting down the office would not absolve the US from its need to fulfill these policies. It would just reduce the presence of the USA on the world stage in the subject area of planetary protection. They would no longer have anyone of their own to do this, and would need to ask in experts from other countries, just as the UAE asked Cassie Conley for advice for planetary protection for their Mars mission proposal. With no planetary protection officer of their own, then they might have to get in the ESA planetary protection officer to help assess whether their missions comply with the international standards. They would have to find some way to do this anyway.

The office performs a vital role, including also, not least, the public outreach.

Also - this is something that will affect us all, not just space colonization advocates. If we return something from Mars that has an adverse effect on ourselves, our animals, crops, or the biosphere of Earth then we are all impacted.

In the other direction too, if we introduce Earth microbes to Mars and this makes native Mars life extinct, the loss of knowledge and understanding of extraterrestrial biology is something that will impact on us all too.

What these hopeful Mars colonists might do, by boldly rushing ahead without taking precautions, could destroy a priceless opportunity for advancing our understanding of biology. The microbes on Mars might look the same externally, but there’s the potential there for a whole new world of biochemistry inside every cell. Something we could never reproduce in a laboratory.

Also, for anyone not excited by the prospect of learning fundamental new things in astrobiology, if we contaminate Mars with Earth microbes, it could also destroy future billion dollar industries that we don’t even know about yet.

The reason your washing powder works so well could easily be because of work done by astrobiologists on Earth, looking for microbes that might meet similar challenges to extraterrestrial life. The enzymes that make our detergents active in low temperature, and even cold water come from cold adapted microbes not unlike microbes we might find on Mars.

The use of extremophile enzymes is already a billion dollar scale industry on Earth, used for lower temperature detergents for our washing, for bread making, fruit juice clarification, wood pulp and paper processing, in textile, cement and cosmetic industries.

That’s from products of extremophiles on Earth. What kind of industries might spring up from enzymes and other produce from extremophiles that have evolved in the much more extreme conditions on Mars? For more on this, see my Benefits to humanity from astrobiology in my Touch Mars?


I think myself that his forceful arguments give us a great opportunity for public education. A vigorous argument is so much more lively to read, and perhaps even entertaining too.

Now, we do have many other places we can go to in space where everything is pretty easy. His ideas do apply, just not to Mars.

That’s true of the Moon especially. Our microbes can’t survive on the Moon and scientists are pretty sure there is nothing on the Moon that is a hazard for Earth.

The smaller asteroids are fine too, and there are many of those in orbits that take them close to Earth. Mercury is fine also, and Callisto (probably), because even though it has an ocean, the surface layer of ice seems to be geologically ancient, one of the most cratered regions in our solar system.

The moons of Mars are fine too. There are many places in our solar system that don’t need protection in either direction.

However, unfortunately he and his fellow Mars colonization enthusiasts have their hearts set on Mars. If you were asked to find the place in our solar system which is most likely to be vulnerable to Earth life, Mars would be one of your first choices (at least since the recent discoveries since 2008).

It is also one of the most likely places to stumble across microbes harmful to Earth, if there are any such, anywhere in our solar system.

There are a handful of other places where we have to take care, including one of Jupiter’s moons Europa, and one of Saturn’s moons, Enceladus. Some would say they are more likely to have life than Mars, but the reality is that we just don’t know, We certainly have to take as much care with them as for Mars and indeed perhaps more so because they have icy surfaces, subsurface oceans and water breaking through to the surface as geysers. It’s a tough job to design a lander that won’t contaminate ice or an ocean.

However, there are no plans to send humans to any of those places in the near future. For those it’s mainly an issue with robotic sterilization. Mars is the only place with potentially significant issues of this type for humans in the near future. It’s the only place anyone is talking about sending humans to in a serious way right now, apart from the Moon.


I suggest we pivot to the Moon. NASA is the only space agency that has Mars as its destination, the only space agency with the aim to go there first before the Moon. And NASA is showing signs of pivoting to the Moon. Also SpaceX is the only commercial space company with similar aims (the others all have sights set firmly on the Moon) and it also is showing some small signs of a pivot to the Moon.

Let’s go to the Moon first and test our ideas there. Let’s go there to learn how humans can survive long term in conditions that are as harsh as further afield in the solar system, but also close enough so that we can have lifeboats to get back to Earth within a couple of days.

Inside look at one of the ideas for the ESA moon village, using 3D printing on the Moon for the radiation shielding. Image credit Foster + Partners / ESA. Their new director, Professor Johann-Dietrich Woerner is keen on taking us back to the Moon first, and has an exciting vision for a lunar village on the Moon as a multinational venture involving astronauts, Russian cosmonauts, maybe even Chinese taikonauts, and private space as well.

The Moon is actually perhaps one of the most habitable places in our solar system outside of Earth itself.

Nowhere out there beats Earth. Even our harshest deserts, the ocean floor, an island covered entirely in a glacier, the top of Everest, all of those places would seem an absolute paradise to a space colonist if they were duplicated in space somehow.

Bouvet island in the southern hemisphere, southeast side, as seen at sunrise, eight miles distant. Black and white photograph coloured by hand. Photo taken on the German Valdivia expedition. It's the most remote island in the world.

It's in the middle of nowhere. The closest large land mass is Queen Maud Land in Antarctica is 1,700 km away

Location of Bouvet island shown with a red dot, map from wikipedia.

It's wide open to colonization as it's not governed by the Antarctic treaty. It's owned by Norway. It has a land area of 49 square kilometers and 93% of it is covered by glacier. This is one of many uninhabited islands on Earth, and I chose it as the one that is closest to Mars in habitability and remoteness, given that Antarctica is off limits because of the treaty.

If Bouvet island was on Mars, the Moon or in space, it would be the most habitable place in the entire solar system apart from Earth and would seem like a paradise to space colonists. It's surrounded by liquid water, salt available in the water, masses of pure water ice in the glacier, breathable atmosphere, fully pressurized so no need for spacesuits, full Earth gravity, already protected from cosmic radiation and solar storms. Very easy access from Earth, just need to send goods on a boat, can get there in days, and, of course much faster with the modest outlet (compared to space projects) of building an airstrip there. It's much warmer than Mars too. They would probably be drawing up plans to cite a city of a million people there. It would be a far more hospitable place for Elon Musk to send his million colonists than Mars is.

You wouldn't need to fish, though it has abundant krill. You'd just set up home there, build your Mars / Moon colony type habitats, heated greenhouses to grow your food and you'd feel you were in paradise :). Yet it is uninhabited and Norway has no interest at all in colonizing it.

We won’t find anything as habitable as Bouvet island in space. But the Moon is perhaps a good second best, with its solar power 24/7 at the poles, almost year round (just a day or two without the sun), and ice nearby in the craters.

It has constant temperatures without the extreme day / night cycles of Mars, which makes engineering easier. The close to 24 hour day on Mars is actually an engineering challenge rather than an asset.

Heat rejection is often a big problem for a space habitat to stop it overheating. That’s simple at the lunar poles - radiators spread out on the surface will never be touched by the sun’s rays and so have constant heat rejection with no need for tracking at all.

Sun tracking is simple too with solar panels or a light collection system that rotates slowly about a vertical mast once every 28 days. There are no dust storms to obscure the sun.

The lunar dust is a known problem too. We already know that it is not seriously hazardous to humans on short timescales. It doesn’t make us vomit or lose consciousness, which Mars dust just possibly might. We also don’t need to worry about it moving in the wind, and can surround a base with lunar glass to keep the dust away.

The gray surface of the Moon is actually a good sign. Mars looks reddish in colour because it is covered in iron oxides, but those are not easy to work with. The Moon has pure iron in its place, including nanophase iron in the dust. This makes it possible to melt the dust using a microwave, as easily as you can boil a kettle. The lunar vacuum also is an asset. We can actually make solar panels directly on the lunar surface, melting a few microns of glass, and depositing silicon on top of it to make the cells. A solar panel paving robot could make a one megawatt plant given a year to work on it.

This is a report from the Center for Advanced Materials at the University of Houston, suggesting the possibility of an autonomous solar powered lunar photovoltaic cell production rover

It would use silicon extracted from lunar materials to make the cells themselves. There are various ways you can do the extraction, and, magma electrolysis may be best. The panels then are based on low efficiency silicon cells vacuum deposited on glass. This is not easy to do on Earth but would be possible in the ultra high vacuum conditions on the Moon. Techy details of this suggestion are here. It would require transporting a small mass to the Moon in the form of the rover which then over several years of driving could build a one megawatt facility on the Moon.

The Moon is an engineer’s paradise in many ways. Lubrication need not be an issue as there are vacuum stable light oils. The carbon dioxide on Mars is not much of an advantage as usually carbon dioxide is a waste gas to be scrubbed. So long as you import more food than you grow yourself, then the way the equations work is that you breathe out more carbon dioxide than the plants can scrub from the atmosphere. Plants only need it in trace quantities anyway, 0.04% of the atmosphere. A few kilograms of carbon dioxide is all your habitat needs.

Then Hoyt’s cislunar transport system can let us transport materials from the Moon to LEO, and back again, powered by the movement of materials down the gravity gradient from the Moon to LEO. Mars has nothing like that. The Moon is at a fixed distance. His lunar tether can be built with existing materials. It doesn’t require anything exotic like carbon nanotubes. It masses only seventeen times the payload mass. Once it is in place, you would no longer need to use rockets to land on the Moon or take off from it. His orbital tether in LEO is low mass also. Once we have regular transport back and forth between the Moon and Earth, it won’t take that many flights before this is an economical way to do it. And after that, it’s essentially free as far as fuel costs go.

For details see the Exporting materials from the Moon section of my Case for Moon First.

The Moon is far safer too. We know we can do it. The Apollo astronauts made it seem easy, however they were test pilots able to take tremendous risks with a cool head. To go to the Moon, if we do it carefully, is risky but we can do it. To go to Mars right now, I think borders on reckless.

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"

Chris Hadfield: "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."

Then for Mars, let’s explore it via telepresence from orbit once we are able to go that far safely with humans, meanwhile from Earth. Telepresence with haptic feedback and binocular 3D vision, broadband communication from Earth. We have never done anything like that in space - but we do it all the time on Earth. We can even do surgery at a distance of thousands of kilometers using these methods. Let’s see what we can do on Mars.

We can use many of Zubrin’s ideas on the surface to support rovers there, which we control from orbit using humans in habitats either on Phobos or Deimos or in orbit around Mars. From orbit Mars looks rather Earth like and you are above all the hazards and issues of sun occluding dust storms, and don’t have to put on a spacesuit to explore Mars, have no problems of hazardous dust and perchlorates. And it’s easy to get back and forth between Mars orbit and Earth, far easier than to the surface.

If we explore Mars via telepresence, from orbit, we can be there in person without these possibly devastating consequences of touching Mars.

12th April 2011: Cady Coleman takes pictures of the Earth from inside the cupola.- 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. One of the orbits suggested for exploring Mars is particularly exciting, the sun synchronous Molniya orbit. It comes in close twice a day, approaching opposite sides of Mars, always with Mars lit up by full sunshine. It's an orbit that skims close to the ice caps of Mars on the way in and out each time, much like the view in this photograph. It flies low over the surface of Mars when closest to the planet. Then as it recedes, Mars dwindles to a distant planet, and the cycle repeats twice a day. It would provide great views of Mars, continually changing, in an exciting orbit.

And let’s actually make a start on a biological exploration of Mars.

So far all of this discussion is based on complete ignorance on the part of humanity of what is on Mars. Is there life there? Are there habitats for life there? We still don’t know.

So, let’s find that out first. We can crack this if we do a vigorous - but careful - study of Mars from Earth and eventually with humans in orbit around Mars to help speed it up.

Once we’ve done that, then we can make informed future decisions based on knowledge instead of hypothesis, and established facts instead of hopes or fears.

At that point, the future may become so clear we are all in agreement. Or perhaps not. We will just have to see. But I think it is just too soon to have this conversation and hope for widespread agreement right now. We just don’t know enough to do that.


This must be one of the first books for the general public entirely devoted to planetary protection issues. I was surprised to find very little else, apart from Michael Meltzer's When Biospheres Collide, which is a history of NASA's planetary protection programs, published in 2010, and the technical books written for scientists. That’s the main reason I decided to write a book about it myself, for the general public, available on kindle and also online.

So for more on this suggestion, and more background, see my Touch Mars? Europa? Enceladus?: Or a Tale of Missteps?, on Amazon

It’s also available to read online for free on my website - it’s over 1800 pages, in the kindle book format, with many images. So be patient, as this page has all that in one page and so it takes a while to load: Touch Mars?


For my other books see the Bookshelf of my Kindle books on Amazon. Some are very short, some are long. I have three full length books on humans in space and planetary protection issues. The other two are:


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My aim here is to get readers thinking. What are your thoughts? Do say in the comments. Also if you spot anything to correct here, however minor, do be sure to say. Thanks!

to say. Thanks!