No Simple Genetic Test To Separate Earth From Mars Life - Zubrin's Argument Examined

NASA hopes to go full speed ahead with its "Road to Mars" to land humans on the planet, and Elon Musk wants to build a city of a million on Mars by 2100, but it is rare for anyone in the debates to mention planetary protection. I think many assume it has already been dismissed by simple arguments like this one of Zubrin's - but far from it. As some of the listeners said to me when I was guest on the Space Show last Monday, the disconnect is enormous.

This is an argument Robert Zubrin often uses in his talks to say why he thinks it doesn't matter if we introduce Earth life to Mars, mixing Earth and Mars microbes. He thinks that if we do that, we will still be able to study Mars life and will find it easy to tell which life comes from Mars and which life comes from Earth by sequencing its DNA.

It seems an impressive argument at first. It's often cited as a knock down argument in discussions about whether colonization of Mars would get in the way of the scientific search for life. But when you learn about microbial dark matter, or gene transfer agents, or the possibility of earlier pre-DNA life on Mars, or find out about the actual instruments we plan to use to search for life on Mars, it is not so impressive, indeed it has no force at all really.

So why not? Let me explain. I hope this will lead to more informed discussion in these debates.

There are many possibilities so best to look at them one at a time.

MARS LIFE BASED ON DNA

First - let's take the case where Mars life is based on DNA but has a common ancestor way back, say over three billion years ago, the most likely time for life to be shared between Earth and Mars.

Well in that case, the most likely life we find on Mars are the archaea. Zubrin is right that we have sequenced the DNA of anthrax and many other microbes of special interest to humans. We'd certainly spot anthrax on Mars, but it is not a likely thing to find there (there are no livestock on Mars, we can be pretty sure).

But we have not sequenced many other microbes at all.

MICROBIAL DARK MATTER

First, the number of microbe species is too vast. There are millions of species of multicellular lifeforms, with estimates of the total number of species varying from half a million to 100 million in this survey of census attempts done in 2014.

But when it comes to microbes, and particularly the archaea, amongst the most likely to be shared with Mars, then there are far more. Some think of the order of trillions. Actually the concept of a species is fluid with archaea as they reproduce asexually, and also exchange DNA fragments with each other freely so there is a lot of horizontal gene transfer. There is no clear cut way to define species.

Also many of the archaea can't be cultivated. For instance they may be able to survive only in communities of several species of microbes together and can't be cultivated in isolation. It is hard to sequence a non cultivable microbe. Indeed in most populations of microbes, 99% of the microbes by number are not cultivable,. This is the problem of the so called "microbial dark matter". (Nature article, microbialdarkmatter.org)

It's an ancient lineage, and it has split into many different forms, In The status of the microbial census: an update (Feb 2016), the authors say that among the 65 bacterial phyla, 24 have no cultured representatives and 14 of the 20 archaeal phyla have no cultured representatives (see page 9 of the paper).

There and phyla are at a similar classification level to the chordata, one level above creatures with backbones. So to date, 70% of the archaea phyla have no cultivated "species" at all, and around 39% of the bacteria phyla likewise.

The Earth Microbiome Project is an ongoing attempt to characterize the diversity of the global microbial populations.

SO IF LIFE IS RELATED, VERY UNLIKELY THAT GENE SEQUENCING WILL TELL US IF IT IS FROM EARTH OR MARS

Given the myriad of archaea, and the difficulty of isolating most of them and extracting their DNA and sequencing it, how would we find its Earth cousin, even if it came from Earth in a spaceship?

We could of course do a spaceship microbial inventory of every ship to Mars - all the air, water, food, the microbiomes of all the humans on board etc. But when it comes to the archaea we'd still only have a bunch of DNA fragments that come from some of the archaea on the ship, and no way to enumerate them all.

How could you ever tell if some DNA from a new archaea identified on Mars was somewhere amongst that population of tens of thousands of species of archaea represented by just a few DNA fragments for the entire population?

When they do inventories of microbes in spacecraft assembly clean rooms, they focus on the cultivable microbes so only 1% of the population. For the others, they just find a few DNA fragments and try to estimate a few things about the population, they can't really say much about what they are and what their capabilities are or anything with present day technology. And that's in clean rooms - of course much wider variety than that in a human occupied spaceship.

GENE TRANSFER AGENTS - HYBRID OF MARS AND EARTH DNA

Also if Mars life is related to Earth life, even from billions of years ago, then all the archaea are able to transfer gene fragments using GTAs - Gene Transfer Agents.

This is something they can do with astonishing rapidity. In one experiment done in 2010, then bags of microbes collected from many different sea bed and shore locations were given a GTA to confer antibiotic resistance. They had no reason to need this capability. But by the next day, 47% of the microbes in these bags had taken up the antibiotic resistance.

Bags of sea water - after adding GTAs to convey antibiotic resistance, 47% of the archaea had acquired resistance after 24 hours.

So after introducing Earth life to Mars you would be bound to end up with hybrid life that consists of Mars life with gene sequences from Earth and Earth life with gene sequences from Mars, and this could happen quite quickly, if they inhabit the same habitat and it's a liquid habitat like sea water, as is quite likely. So that also makes the whole thing even harder.

LIFE THAT GOT TO MARS FROM EARTH LONG AGO

It's even more problematical if he is right that Mars and Earth shares a lot of life via meteorites, then that makes it even harder.

Most microbes couldn't withstand the rigors of space in transit to Mars.

But there are some very hardy ones that could be transferred. For instance chroococcidiopsis.

Photomicrograph of chroococcidiopsis

This is an extremophile cyanobacteria that can handle just about any environment you throw at it on Earth. It's thought that it probably was one of the microbes responsible for bringing oxygen to Earth. So it is billions of years old and over that timescale has developed an incredible number of metabolic pathways.

It can handle

salt water
hypersaline water
fresh water
hot springs
Antarctic ice and dry Antarctic rocks
conditions of only 60% humidity and no rain at all in the Atacama desert in salt pillars
just fine in nice warm pleasant conditions too, such as the tropics, e.g. Sri Lanka.
protected against extreme ultra violet light
is able to withstand Martian UV levels in partial shade and even photosynthesize and metabolize in those conditions
can handle the Mars near vacuum atmosphere as well
and may be able to grow on Mars without water, taking up moisture from the 100% humidity at night - according to experiments in Mars simulation chambers done at DLR.

(There are many strains of chroococcidiopsis, so in those experiments they used particular strains they expected to be particularly good at dealing with those conditions).

And in addition to all those talents, it is also a radioresistant extremophile, able to repair its own DNA when damaged within hours. It just fits the fragments back together again when they are broken up by the ionizing radiation. There's no reason why it would be able to do that - except perhaps as a side effect of desiccation resistance.

So - that's one of the few microbes we have that I could imagine being shared with Mars. Because - they have to be able to handle the vacuum of space, shock of ejection and hitting Mars, ionizing radiation during the minimum of one century transit time as estimated for ejecta from giant impacts on Earth large enough to send meteorites to space through the atmosphere.

And then they have to be able to survive on Mars when they get there - much easier in the early Mars with oceans or lakes on the surface.

So, suppose it has got to Mars on one of the impacts in the early solar system?

It's bound to have evolved a fair way compared to Earth strains, in the strong UV light there, the ionizing radiation, the near vacuum conditions.

Even if only introduced 66 million years ago, sent there on debris from the forming Chicxulub crater, it's bound to have evolved a fair bit in such different conditions. And more likely has been there evolving separately for billions of years, if it is there at all, as the best chance by far to get there is in the early solar system.

So it would then resemble the Earth variety, yet not quite the same. Again the last thing you want to do in this situation is to introduce a modern Earth strain that has evolved its own new capabilities in some other evolutionary path.

LIFE THAT IS LIKE EARLY EARTH LIFE, RNA ONLY, AND MORE FEEBLE

But worst of all - all that is based on the idea hat Mars life resembles modern Earth life.

But what if it isn't?

First, what if what we have there is some very feeble early form of life?

Say with RNA and the much smaller ribozymes (instead of the more usual huge ribosomes) in a tiny 50 nm cell of only 1000 ribozymes as suggested in the 1999 workshop on limitations of size of living cells?

See Constraints on Size of a "Minimal Free-living Cell"

We can't make such a cell. It is way beyond our capability to engineer something so complex from scratch - but we do have both RNA and ribozymes and it seems that theoretically such a cell would work. And then also, whatever it might be, the smallest DNA based cells, the ultramicrobacteria are still 200 nm in diameter. Something so complex has to have had more primitive precursors. This RNA cell with ribozymes is one of our best guesses at what its precursors were.

That tiny cell might well work fine on Mars, Indeed, if you are one of those who believe that ALH84001 has fossils of Mars life (the debate still is open) then that would mean we have fossils of living cells this small from Mars already.

Structures on ALH84001. The debate about whether this is fossil life or not continues. If it is life, the cells are too small to contain all the machinery of modern life so must be some other form of biology, possibly earlier forms of life.

And perhaps it could co-exist with some Earth lifeforms.

It might perhaps co-exist nicely with Chroococcidiopsis for instance. Chroococcidiopsis is a prime producer, and doesn't need to eat any other microbes. It just uses CO2, sunlight, and rocks, and water - that will do it just fine. It's one of the few species able to create single species ecosystems - to add to its list of talents. In the Atacama desert, there are many salt pillars where the only species is Chroococcidiopsis.

So on Mars it might play nicely with many other microbes so long as it is not in competition with them - perhaps even perhaps with early vulnerable Mars life. It might even be a food source for it.

But the early life could be very vulnerable even to chroococcidiopsis if they are photosynthetic lifeforms in competition, or for some reason chemicals it produces are toxic to them.

Also, supposing Chroococcidiopsis was already there, there could be species introduced from Earth that were not able to get there in a meteorite, but well able to survive there once introduced. Either just competition from the many primary producers introduced by the spacecraft - or else, directly by new anaerobic secondary producers that can eat them.

These early micromartians might be easy to eat. They might have no defences against more modern DNA based life.

So early life there could be vulnerable even if it already co-exists with some Earth originated life there.

It might be possible to distinguish it, but that's no use if it goes extinct after introduction of Earth life.

Then there's the interesting possibility of something even earlier - RNA or other self replicating polymers without any life in the organics of Mars. Or autopoetic cells.

Or any form of complex organic chemistry in an environment without life. In that case it would be of huge interest to exobiology and yet so fragile and easily destroyed by introduced Earth life. It could be completely gone before we are able to discover that it is there.

With the hundreds of miles an hour winds in the dust storms every two years in the southern summer, then exponentially growing populations, if they find easy uninhabited habitats to colonize on Mars, or habitats with only life precursors or very early life - could get to them all quickly, faster than humans can get to them to study them before they are gone. Even if we did manage to study some of them before they are all gone, it would still be a tremendously sad outcome for our search for present day life on Mars.

Zubrin thinks that early life may exist on Mars, but that if so it probably co-exists with modern Earth life there (see 40 minutes into this spaceshow talk for instance). And that if so it wouldn't be vulnerable to modern life introduced from Earth. If that whole picture is correct, then this is not a concern. But with the other picture, that it probably existed on Earth as well and was out evolved by more modern life, but is still there on Mars, then it would be very vulnerable.

But for a different view here, most theories of abiogenesis are based on the idea that there were earlier forms of life on Earth, for instance RNA based or using the more robust TNA, or PNA, or autopoetic cells, that were made extinct by later DNA based life.

DIFFERENT BIOLOGY E.G. XNA INSTEAD OF DNA

As for a different biology, say XNA based - yes you'd be able to distinguish it form Earth based life by various methods depending what it is.

But:

First - our experiments we want to send to Mars to detect past and present Mars life are exquisitely sensitive. They can detect a single amino acid. They will be looking for small signals. E.g.

Searching for chirality imbalance in amino acids. Which then would need to be analyzed carefully as asteroid amino acids also have chirality imbalances, to see if it is an asteroid amino acid or life based amino acids. The life based would be 100% of one chiral isomer - but if it is past life it is decayed, deracemization means it is no longer 100% and the percentage changes depending on how long it has been buried. And you may well have a mixture of past life, and past organics from meteorites.

If present day life, then similarly it could be mixture of the present day life and meteorite organics. Present day Earth life would make this approach totally impossible to use.
Searching for redox reactions in a microbial fuel cell - to detect if there is any life there at all. This will not be able to distinguish Earth from Mars life at all.
Chiral labeled release. Again present day life would make it unusable.
Searching for biosignature molecules. You couldn't use this to test for any biosignatures that are shared with the present day Earth life there.

It would leave few approaches you could use. DNA sequencing, or XNA sequencing of course. And there might be other biosignatures you could use. And no way to study the behaviour of the XNA life as it was before it got mixed up with DNA based life. E.g. if it used to form XNA based microbial mats or complex lifeforms made up of colonies of XNA based life, or whatever.

DNA LIFE COULD OUT COMPETE THE MARS XNA - OR VICE VERSA

And as with RNA based early life, if we find XNA based life, also, then you have the same problems as for early life. That it is adapted to live on Mars does not at all mean it will survive competition with Earth life. We've already seen how if it is some very early feeble form of XNA based life with tiny 50 nm cells like the ones in ALH84001 if those are indeed life, it might not survive encounter with Earth life at all.

If it is more advanced than those early cells, well it could still be billions of years of evolution behind Earth life (I mean that if it evolves more slowly on Mars could be it still has billions of years to catch up) or billions of years ahead of us (if Mars conditions have hastened evolution so Earth life needs billions of years to catch up) - very unlikely to be at the exact same stage of evolution.

And it could be more efficient or less efficient than Earth life, better or worse at photosynthesis, more or less efficient cells etc.

DNA LIFE DOES NOT NEED A KEY TO XNA LIFE OR VICE VERSA

This is another of Zubrin's arguments - that life to be a nuisance needs a "key" and to be co-evolved. But there are plenty of counter examples here. It is not at all plausible that viruses based on XNA could be harmful to DNA or vice versa. But there are many other ways that lifeforms can harm each other.

First, pathogens adapt to their hosts to be less virulent, usually, not more so. It's in the interest of a pathogen to keep its host alive as long as possible. Eventually they may co-evolve to the point where the former pathogen becomes a symbiont. Pathogens are often at their most virulent when they first encounter a new host.

For example legionnaire's disease is actually a disease of amoebae. It's adapted to eat amoebae from the inside. It's actually many different microbes though 90% of the cases are one species. And it is caught from infected water, not from other humans. As far as the disease microbes are concerned, then the macrophages in our lungs - the large white blood cells whose job is to eat foreign matter and other microbes - resembles amoebae. It's not keyed to human DNA at all.

Then, it might be that Earth life can detect XNA based life as a threat and protect itself but the XNA based life has no defences against DNA based life. Or the other way around Earth life may not be able to recognize XNA based life as alive enough to try to do anything about it. Either way around the more vulnerable of the two could just roll over and let itself being eaten saying "Hello friend" or even "Can't see you".

This is an insight from the biologist Joshua Lederberg who got the Nobel prize for his work on bacterial genetics. He wrote (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."

He wrote that about the reverse direction, from Mars to Earth, but it applies both ways. Similarly Mars life might not be adapted to defend itself against Earth life. So though Earth life would not be adapted to attack Mars life, nevertheless, the Mars life might also not recognize Earth life as a threat, so not be adapted to protect itself against it either.

The thing is that if there is some other form of life on Mars, then it may never have encountered anything resembling Earth life, and vice versa. The space of possibilities for evolution to primitive life from non living chemicals is likely to be so vast, that there is no way either could have explored all the possibilities.

And it doesn't have to be eaten by Earth life. It is enough if the Earth life grows more rapidly and is more efficient at using the available resources - or else - produces chemicals that are toxic or inhibiting to Mars life. E.g. the Earth life changes the chemistry of the water in a way that makes it no longer habitable to Mars life - then the Mars life would soon go extinct.

There is no way of knowing what would win in a battle for survival in a small solution of salty water with a mix of Earth and Mars life on Mars.

So - those are some of the main points.

I posted this originally as a reply to my SpaceShow guest appearance comments. But it's a bit long and better to post here. And it is such a frequently discussed topic, and a commonly used argument of Robert Zubrin's I think it is worth a separate article.

The reason for saying this is to encourage debate.

ZUBRIN'S ARGUMENT IN HIS OWN WORDS

This is from an interview with Robert Lamb

“In exploring for life on Mars, you do want to avoid any confusion caused by terrestrial life that you bring with you. However, properly designed experiments can distinguish the two. If you were exploring some island in the South Pacific and discovered a purebred beagle, would you assume that it evolved locally or that it had escaped from a passing ship or something? It’s clearly something that came from abroad. On the other hand, if you discovered a dog of previously unknown breed there, you’d have reason to believe it originated locally.

“Similarly, do you remember back to 2001 and the anthrax scare? They were able to look at that [strain of] anthrax and say not only that it was anthrax and not some other microorganism, but that it was anthrax that came from a particular lab in Iowa. Not only that, but the genetic drift from the base stock in the Iowa lab indicated that it had probably been taken from the lab in the mid 1980s. They were able to determine all of that.

“So in other words, microorganisms are not generic. They’re specific, just like beagles. If we go to Mars and we discover a variety of microorganism that is identical to something in an Iowa laboratory, then we know this thing came from Earth. On the other hand, if we find a microorganism on Mars that has a different genetic structure than anything we know on Earth, then we know it didn’t come from Earth. So that’s not really an ethical question, that’s a practical question.”

ZUBRIN'S PANSPERMIA ARGUMENT

I'll just go into this briefly. Zubrin often cites the idea that Earth life is identical to Mars life due to panspermia - spread of life by meteorite impact. This came to prominence when it was put forward in a paper to Nature Geophysics, called "The Overprotection of Mars". by Alberto G. Fairén & Dirk Schulze-Makuch. This got a lot of publicity.

Hardly anyone seems to have read the rebuttal by the planetary protection officer Cassie Conley, "Appropriate protection of Mars" which was published in Nature a month later. There are many holes in the argument in "The Overprotection of Mars" - assumptions they make that can be questioned. This argument is cited over and over by Mars colonization enthusiasts and probably almost none of them have read the rebuttal.

You can read a summary of both papers in this article "The Overprotection of Mars?" by Andrew Williams in NASA's online astrobiology magazine at astrobio.net

And indeed - on this panspermia argument, even on Earth, the microbes in Antarctica are not identical to those elsewhere - visitors to Antarctica are required to disinfect their boots on landing, and that's not just to keep out invading plants and small multicellular life, but also to preserve its unique microbiology communities. It's not that often that we have to be careful about microbes here on Earth but we do sometimes .There are also concerns like that for some cave communities of microbes.

So - with even variations on Earth of microbial communities - how likely is it that life on Mars is identical in all respects? Most exobiologists would be astonished and want to keep Mars free of Earth life to study this extraordinary situation and tease out what differences there are, as surely there would be over billions of years independent evolution in a radically different environment from Earth.

But which lifeforms from Earth could get there anyway? Only life able to withstand the shock of ejection from Earth, the vacuum and cosmic radiation of the 100 year transit to Mars, the impact landing on Mars - and then find a habitat they can survive in on Mars too. There are some microbes that could do this in theory, whether they can in practice is not yet known. But whatever got over there, if anything has - they are hardy cookies! Hardly a representative sample of Earth life. And then have to evolve in cosmic radiation, solar storms, UV light, perchlorates and hydrogen peroxide, for at least 66 million years since the last chance to get there. It's not a compelling argument, the idea that the life there has to be identical to Earth life.

The best time for life to be transferred from Earth to Mars, or vice versa, was during the "late heavy bombardment". Panspermia remains a theory and though there are some microbes that our calculations suggest could be transferred, we don't yet have an example of life transferred in this way.

For more on this see my: "Does Earth Share Microbes With Mars Via Meteorites - Or Are They Interestingly Different For Life?" and Could Microbes Transferred On Spacecraft Harm Mars Or Earth - Zubrin's Argument Revisited

APPEAL OF ZUBRIN'S IDEAS

I can understand that Zubrin's arguments are enormously appealing to those who want to land humans on Mars. If the universe was set up in such a way as to be perfect for human colonization, this is how you would make it, make it so that humans can go anywhere they like in the galaxy and they won't cause any harm to anything.

But we have made many mistakes on Earth, made species extinct by introducing rats, dogs, rabbits, and other creatures to islands and continents. So - I think it is clear the universe is not set up in such a way that humans can't make mistakes. And introducing Earth life to Mars could be one of the biggest of those mistakes ever, if he turns out not to be right.

PRO SCIENCE, NOT ANTI SPACE SETTLEMENT

I write this from the viewpoint of someone who thinks humans in space are cool, who loves science fiction, but who is also passionate about science too and sees exploration in space as a new scientific discovery frontier, not just a new human occupation frontier.

If human occupation actually retards and prevents this movement into the frontiers of scientific discovery - then for someone who loves science, space exploration actually loses pretty much its entire point. It could even be something you want to prevent - rather than something to celebrate and see as a great thing we are doing.

As you'll see from that talk if you listen to it and my articles here, I am not at all anti colonization or anti space settlement. I see them as somewhat neutral actually, can be used for either good or bad, but have a lot of potential for good if well used.

But I also think that Mars, like Europa and Enceladus, are the three most interesting and most vulnerable places in our solar system for exobiology.

So the reasons for saying these things is just because I am pro science and keen on exobiology. It's what I would call a superpositive outcome. In the best case our discoveries there would be of outstanding interest to biology and astrobiology. Then because biology is of such importance - we are surrounded by the products of biology - it would in best case also be of supreme value for agriculture, medicine, nanotechnology, and technology generally also using the products of exobiology whatever they might be.

We must not, in my view, mess up Mars by introducing Earth biology before we know what is there. That would divide Mars into two eras - the first over four billion years with whatever is there now, then the future millions, and billions of years with Earth life there. This would impact on the studies of Mars and exobiology not just for ourselves but our children's and grandchildren's generation and so on through all future human civilizations and all future civilizations by all other intelligent beings that might arise on Earth for all future time.

Zubrin thinks that Mars and Earth life is likely to be identical due to microbes transferred on meteorites. Even if he was right, that Mars life is identical to Earth life - this would be a discovery that would astonish astrobiologists. We'd want to find out how this remarkable thing happened with so little interchange of life between Earth and Mars.

So, another view on this - the last thing we'd want to do is to introduce Earth life until we figure out how it happened. It is hard to think of a scenario that would lead to the conclusion that introducing Earth life to Mars is of no significance to exobiology - not until we have a chance to explore Mars thoroughly and find out what is there.

Once we understand what is on Mars thoroughly - at that point we could think about it on a basis of understanding Mars well, whether or not introducing Earth life to Mars, intentionally or accidentally, is acceptable. At that point it would be on a basis of knowledge and understanding, and that changes everything.

LEGAL FRAMEWORK

NASA also has a strong mandate for science. If this conflict does arise as I think is possible, as I say in the talk, there is no way they would choose to support colonization against science.

Robert Zubrin is also very keen on science too. He thinks there is no conflict and can be no conflict. He's certainly not anti-science. If COSPAR came to the conclusion that there is a conflict, he'd be arguing against that conclusion. But he wouldn't be arguing that we should go to Mars and just not be bothered about the science. For him one of the main motivations he gives to send humans there right now is to find out about the biology there.

Also, by the Outer Space Treaty also, all countries who joined that are mandated to protect celestial bodies from contamination that is harmful to scientific work by any of the signatories to the treaty. At any rate that is how the clause IX is universally interpreted. And no country would withdraw from it - that's inconceivable. It's the reason the Apollo astronauts could say that they came to the Moon in peace for all mankind.

Without the OST they would have had to say they came to claim the Moon for the US, as was indeed the original plan before the OST was signed, with detailed plans drawn up for a base on the Moon to fight off all other nations who tried to claim it for themselves. Those plans were perhaps not very practical but it is the idea behind them that counts.

It is a remarkable treaty that, through design or other I don't know, shaped all space flight since then. It's the reason we can have friendly competition in space and are not concerned that e.g. China has designs to claim the Moon for itself. It prohibits weapons of mass destruction in space also. It is hard to pass such a treaty as the Moon treaty shows, signed by only a handful of nations. While the OST is signed and ratified by all the countries with space aspirations, including North Korea, only Syria of countries with any aspirations in space at all has not yet ratified it, and Syria too has signed it, and would surely ratify it if it makes more progress in space technology. Most nations with no space technology have also signed it and most ratified it too.

I think the future has to be to work within this treaty, and no country has suggested that it might want to withdraw. That's almost inconceivable. It is flexible enough to act as a legal framework through into the future, by adding new laws, not withdrawing from it.

MANY OTHER PLACES TO COLONIZE OR SETTLE - HABITATS FOR A THOUSAND TIMES THE LAND AREA OF EARTH JUST WITH MATERIALS FROM THE ASTEROID BELT

There are many other places you can try to colonize. Lots of asteroids, that are almost identical and you aren't robbing science of anything if you mine one of the many iron meteorites for instance. There are plenty more where they came from for the scientists. There is enough material there to build habitats with cosmic radiation shielding for a thousand times the land area of the Earth. And the ones that fly past Earth every day - they are temporary - due to be cleared out of our orbit by Earth within 20 million years. Will hit the sun, Jupiter, other planets, ejected from solar system or hit Earth. You may actually be helping remove a future impact hazard by mining them.

See my Asteroid Resources Could Create Space Habs For Trillions; Land Area Of A Thousand Earths

The Moon also - classified as category II for planetary protection. No problem colonizing the Moon.

And humans can also explore Mars via telepresence from orbit, a very exciting and interesting mission. It is like the NASA "Road to Mars", goes all the way to Mars orbit but stops there. With binocular vision and haptic feedback and enhanced vision study of Mars from orbit with robotic avatars on the surface. A spectacular orbit that comes close to the sunny side twice a day, skimming close like the ISS, then zooms away over the polar regions, so far away that you see Mars like a small moon like planet in the sky, then back in again twelve hours later for several hours of close up telepresence, then out again.

This illustrates the orbit astronauts could use for early orbital studies of Mars using telepresence from orbit. It's a spectacular orbit and interesting to the astronauts. Approaches Mars on its sunny side twice a day, then zooms away past the polar regions as the planet dwindles to a small disk in the sky then back in again. You'd see the dust storms, clouds, close up flyby over different parts of Mars every time. And control anywhere on Mass surface with close up telepresence, twice a day.

To Explore Mars With Likes Of Occulus Rift&Virtuix Omni - From Mars Capture Orbit, Phobos Or Deimos

Which is also lower cost, gets much more exploring done as you can control telerobots over the entire surface of Mars by telepresence. And far safer for the humans, as they can stay within their spacecraft while exploring in VR, and return to Earth easily. And no need to build the expensive hardware to land on the surface and return. And broadband streaming of everything the astronauts see and do back to Earth.

You'd stop in orbit around Mars for the same reason the Russians have stopped short of sending a miniature submarine into Lake Vostock in Antarctica below the ice. They would love to send a submarine there. The lake is of great interest, most oxygenated water in the planet probably, and may have hydrothermal vents and may even have unique creatures and microbes. But we don't yet have the technology to sterilize a submarine sufficiently to send it down to see. They did drill through, just enough to get a sudden geyser rise 40 to 80 meters which they then sampled - with the bottom of the geyser freezing over so preventing back contamination (the lake is at a very high pressure from the weight of the ice above it).

For similar reasons, I can't see exobiologists approving a human mission to the Mars surface any time soon. Not now that we know that there is liquid water on the surface and there is some chance that some of it could be habitable - yet to be found out. Plus the global dust storms, making it one connected system for microbe spores.

DISCONNECT AND SHOCK

As some of the listeners said on the show, there seems to be a giant disconnect here. So many people are pressing ahead for humans to Mars in the States, and it is rare that they even mention planetary protection. NASA with its Road Map to Mars, and Elon Musk proposing to send a hundred people at a time to Mars in his "Mars colonial transporter" and create a city of a million people there by 2100.

I was asked several times in the show, why so many bright people don't talk about these issues. I never know how to answer that question. How can I say when they don't say anything about it?

I can say a bit from my own experience though. Until a few years ago, perhaps a decade or so ago, I can't remember when exactly, I gave this no thought either. I was keen on science fiction, and loved the stories about exploring space. If I'd read about his ideas then, I wouldn't have given planetary protection a moment's thought either. It's funny, how you can understand the need for planetary protection for robots easily, and yet, forget about it as soon as you start talking about humans.

So in some cases at least, perhaps it is just like that earlier me, that they haven't given it a great deal of thought. But it's impossible to say, except for those that do explain. Robert Zubrin has given it a lot of thought, and he is keen on science, and he thinks it is consistent with science. So you can say for him. But how can you know, say, for Elon Musk? As far as I know he has never mentioned the topic.

David Livingston said there would be a giant shock amongst all these space colonization enthusiasts, if they found they can't go to Mars for planetary protection reasons. He gave the example of Humans2Mars, h2m for short, who hold a big meeting in the spring with many speakers - and don't have planetary protection as a road block on their map at all.

For more about this have a listen to the show. You may find it challenging. The main reason for posting these things is to encourage discussion.

WHAT WOULD HAPPEN IF HUMANS CAN'T GO TO MARS

I think if humans can't land on Mars, that these people won't just give up. After a period of shock and re-evaluation - well most of what they worked on can be applied elsewhere in space.

For those who are keen on Mars because they are interested in the planet and want to explore it - and super keen on exobiology like Zubrin - they could build in orbit around Mars. Use regolith from Deimos or Phobos to shield their habitats.

Robert Zubrin has pointed out that Deimos and Phobos are difficult to get to as regards delta v. But you can go to a Mars capture orbit instead - that is very easy to get to from Earth, the one I just described. Then shield habitats in that orbit using regolith from Phobos and Deimos, and supply with water from those moons - or else - supply from other asteroids. It is easy to move material around in space if you have lots of time.

They could also get to Mars via ballistic transfer. This is the safest orbit I've seen for human missions. And you can do it at any time, not just once every two years. You launch the mission to arrive in Mars orbit ahead of Mars. The planet then captures your spacecraft into a very distant more or less circular orbit, with no delta v. It is a temporary capture like the temporary few meters diameter moons of Earth that you get from time to time. But then you can move down to lower orbits gently using ion propulsion.

This is very safe for both humans and for the planet. Not like rocket thrusters where a few minutes of extra thrust could mean you hit Mars, and a few minutes too little means you fly off into interplanetary space again.

And since ion thrusters are rather efficient, you could spiral all the way down to Phobos or Deimos. It's not really a saving of fuel if your destination is, say, Deimos. The total delta v is similar to Hohmann transfer. But the use of ion thrusters makes it easier and more efficient - present day ion thrusters are not powerful enough for a normal Mars capture scenario..

Or you could use your ion thrusters to get into an eccentric orbit resembling the Mars capture one by applying thrust only at one point in your orbit each time.

Then Zubrin's ideas for generating fuel on Mars can still be used - but used to power rapidly moving robot avatars on the surface for humans to control from orbit. Rovers you can drive, with binocular so 3D vision, enhanced colours, blue skies if you like, hands you can use to pick things up and feel things (haptic feedback). Indeed by then, we'll probably have walking robots which you could use to walk around on the surface as if you were there yourself. A lot of this technology may come from computer games - there are far more centuries and millennia of developer time put into computer games than into spacecraft software and many computer game innovations may be of great value for space exploration. See my To Explore Mars With Likes Of Occulus Rift & Virtuix Omni - From Mars Capture Orbit, Phobos Or Deimos

His ideas for in situ resource utilization can be used with ice perhaps mined from Deimos and then sent to the settlement using the water itself as rocket fuel. Or similar resources from elsewhere, e.g. NEOs.

As for those who are dead keen on colonization but don't care where they go - or those who are interested in the Moon (much more interesting, also much more habitable, than we realized a few years ago) - they can try to colonize the Moon. Or create habitats from asteroid belts.

I don't think myself that they will succeed at colonization, but rather settlement, as I explained in the show also. Before it becomes as easy as they imagine to set up a space colony we could set up a floating sea city, that just uses sea water and the atmosphere, maybe some rocks also - but gets its metals from the sea water, and is pretty much self sufficient, providing everything it needs. Not fishing, but a floating almost totally self sufficient colony (apart from air to breathe and seawater) like these proposed space colonies.

That would be very eco friendly.

I don't think we are close to this technology yet. I think we will be able to do that and many other things before we can set up self suffiicent space settlements.

For that reason, I think that for the near future, space settlements will exist just as they do in Antarctica and other inhospitable places - either because they are supported by wealthy people, or for tourism, explorers etc, or because they are seen as of benefit to humanity.

There are many such reasons for being in space. But I think for the near future, next few decades, that there will be a many to one ratio between the people on the ground supporting them by making things, supplying food, making rockets, launching them etc, and the people in the space settlements. For instance a space settlement of a thousand people might have ten or a hundred thousand people on Earth supporting them with all the complex machinery and supplies they need and the rockets for transport to and from etc.

And - I think myself that's not a bad thing. I suggest that the main problem with technology is the pace of change, and that if something takes a bit longer than expected, that gives time to work out the implications and learn how to live with the new capabilities. Just as we learnt to live with fast boats, jet planes, cruise missiles, nuclear weapons, biological weapons, chemical weapons, submarines, personal computers, mobile phones, internet, easy ways to cut down entire forests and build huge roads, etc etc. Imagine if in 1900 all of those things were somehow invented in just 10 years?

The world would be in chaos and indeed, might not be too suprising if humans went extinct. With a bit over a century, we have more or less found a way through them all with some problems. I think that we have many more things like this to adjust to in the future - and we'll be able to do so similarly, so long as the pace of change is something we can keep up with as we have so far.

For more on this, see my Can You Suggest A Second Earth Apart From Mars?

SO WHAT DO YOU THINK?

The main reason for writing this is to stimulate debate on these topics, and to help make sure the debate is done with an informed background.

What do you think about these ideas? Do say in the comments.

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