MOON FIRST

Why Humans on Mars Right Now

Are Bad for Science Includes: Astronaut gardener on the Moon Copyright © Robert Walker (UK). All rights reserved.

(See high resolution version of this cover picture)

The cover picture shows Astronaut Eugene Cernan walking towards the Lunar Roving Vehicle during an EVA for Apollo 17, the last mission to land on the Moon - with the black sky replaced by a blue one, and no other changes at all. For the motivation for doing this, see the section below: What if the Moon had blue skies.

Thanks to Nathan Ryweck of Gelato Media for converting my book cover draft into a professional design.

First published: October 2016. You can also get this on kindle. For my other kindle booklets, see my author page on Amazon.com. You might be especially interested in my related books:

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. On windows you can use print (Ctrl + P) then change the printer to the pdf printer. The Print button then changes into a Save button and you can then save it where you want. However the embedded youtube videos won't work if saved as a pdf. If you are techy, you can make the videos in the pdf work as links with preview images. To do that, save it offline as a web page first, then edit the html, remove all the iframedummy tags, and that will reveal images and links that are covered by the iframedummys (done like that for kindle) - which will then work in the pdf. You can also save it as a web page. Most web browsers have an option to save a page as "Web page complete" which includes all the images in the page saved on your computer for offline browsing. Be sure to give it time to download the page before you close the browser tab.

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The main sections in this book are

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I wrote this book after the then President of the US, Obama, in an op-ed, said that he wants to send humans to Mars, because he loves science. Great!. But hardly anyone stops to ask the question: "What would humans landing on Mars do to the science they so love?" The question is especially acute in the case of a crash landing, which is a likely scenario in a landing on Mars, the toughest place to land on in the inner solar system. "What happens to our trillions of microbes if a human occupied ship crashes on Mars?"

Could we find life on Mars, present day life, based on different principles from Earth life? That would surely lead to some of the most significant discoveries in biology of the twenty first century. What would a human crash do to the scientific potential of the planet?

There are three top priority places in our solar system to protect from Earth microbes: Mars, Europa and Enceladus. Why rush humans with our trillions of microbes, as quickly as possible to the one place inside of Jupiter's orbit most vulnerable to Earth life?

And - is this the right time to attempt a colonization anyway? When Shackleton succeeded in overwintering in Antarctica after his ship sunk, he didn't say "Oh great, we have managed to survive here huddled under boats, hunting seals, so we must colonize Antarctica".

In the New World, there were plants to eat, crops could grow, and temperatures were equitable. It had human inhabitants already and you could breathe the air and drink the water. It's hard to beat that. We have never colonized anywhere like the Moon or Mars, far more inhospitable than Antarctica. Even the summit of a mountain four times taller than Mount Everest would be far more habitable than either of them.

Are there other ways forward? Ways that let us explore Mars thoroughly and search for life there, experiment with space settlement and colonization, and protect the science value of Mars? What about exploring Mars from orbit, operating robots on the surface? That's the preferred way forward of scientists who care about planetary protection of Mars. How effective is it? Perhaps it is a more direct and immersive way of exploring Mars than with astronauts on the surface. Do we need astronauts to drill? What about robotic moles? What if we make these orbital missions and missions to its two moons and telerobotic exploration of Mars our long term goal for humans to Mars? What if we leave any decisions about whether to land humans on the surface to a later date?

Also - we have the Moon, right on our doorstep. With the new discoveries of the peaks of almost eternal light at its poles, the radar data suggesting vast caverns over 100 km long, and ice detected at the lunar poles - how does the Moon now compare with Mars? This is the usual focus for Moon first books such as The Value of the Moon, Moonrush, and The Moon: Resources, Future Development and Settlement, and I go into this in some detail as well.

You might be surprised at how well the Moon stands up against Mars in the comparisons. The two week long lunar night is far less of a drawback than you might think due to interesting discoveries about plants kept in darkness for two weeks at a time and modern efficient LED lights, while the peaks of almost eternal light may give a way to build early bases with abundant solar power available nearly all the time.

If you love science, as President Obama does, then do read this book and find out more about the case for exploring the Moon first and protecting Mars from Earth life for now, and make up your own mind.

This kindle booklet brings together material from my recent articles on Science20:

along with material from my longer kindle book Case for Moon First.

Contents

Originally published on my Science20 blog here: President Obama, Why Humans On Mars Right Now Are Bad For Science

President Obama has just taken the unusual step of publishing an Op-Ed article for CNN "America will take the giant leap to Mars". It promotes his vision for humans on the Mars surface in the 2030s. The video at the head of the article highlights his love of science. But what would humans landing or crashing on Mars do to the science he so loves? Unlike a robotic lander, a human occupied spacecraft can't be sterilized of its trillions of Earth microbes, and a crash of a human crewed spacecraft on the surface would end planetary protection for Mars. It's easy to find life if you bring it yourself, but what an anticlimax that would be to all our years of exploring the planet! Here is another video with clips to show his love of science.



(click to watch on YouTube)

President Obama presenting John Glenn with the medal of freedom. He was the first American astronaut to orbit in space.

I never thought of planetary protection for human missions to Mars myself, until a few years back. So, I can understand from my own experience how it is possible to simultaneously agree that we need it for robots, to be keen on science, and yet at the same time, to forget about it as soon as humans are mentioned. Robots can be sterilized. Humans have trillions of microbes on our skin, in our gut etc, and sadly, we can't be sterilized of them. Nor can we replace them all with microbes unable to survive on Mars. Any attempt to remove all our microbes would kill us.

We may be on the point of making the next major discovery in biology. What we discover there could be so major that historians of the future mark out three significant points in biology

The theory of evolution in the nineteenth century

in the nineteenth century the discovery of the double helix structure of DNA in the twentieth century (though DNA itself was actually discovered in 1869 by the Swiss physiological chemist Friedrich Miescher who called it "nuclein")

structure of DNA in the twentieth century (though DNA itself was actually discovered in 1869 by the Swiss physiological chemist Friedrich Miescher who called it "nuclein") The discoveries in exobiology of the twenty first century (which of course lie in our future).

Of course we have no idea what those discoveries will be. We have found many possible habitats for life on Mars, but we have not yet been able to send any spacecraft up close to look at them. Indeed Curiosity may be not far from some of those. If they are indeed possible habitats, it's not sufficiently well sterilized to look at them close up, and at best, it may be able to observe them from a distance of several kilometers.

Discoveries of this sort are what I've called a "super positive outcome". There is no risk to humans from introducing Earth life to Mars, so it's not covered by the precautionary principle. But there is a risk of losing something wonderful and precious.

The exobiologists, who hope to fly in situ life detection instruments to Mars some day, design them to be as flexible as possible, to detect not just familiar forms of life. As an example, Chris McKay with his "lego principle" suggests a general way of looking for life not depending on any assumptions that it resembles Earth life. See his What Is Life—and How Do We Search for It in Other Worlds?

What we discover there could include any of:

Early life, e.g. tiny RNA world microbes without DNA or proteins. There are many ideas for early life that could perhaps still exist there, though extinct on Earth. These could fill in the huge gap between the organics and cell like structures resembling cells that turn up in laboratory experiments, and the immense complexity of modern life. One idea is an RNA world cell with no proteins, or ribosomes either, instead using RNA sliced into pieces and recombined to make a ribozyme, a tinier distant cousin of the ribosome. This is possible in theory, and some have suggested that present day Earth might have a "shadow biosphere" consisting of RNA world cells, but this has never been confirmed. Maybe we can find RNA world cells on Mars instead?



There are many other ideas for early life that could perhaps still exist there, though extinct on Earth, including the so called autopoetic cells that replicate just by producing daughter cells with a similar mix of chemicals when they get large, with no genetic code to regulate the process.

without DNA or proteins. There are many ideas for early life that could perhaps still exist there, though extinct on Earth. These could fill in the huge gap between the organics and cell like structures resembling cells that turn up in laboratory experiments, and the immense complexity of modern life. One idea is an RNA world cell with no proteins, or ribosomes either, instead using RNA sliced into pieces and recombined to make a ribozyme, a tinier distant cousin of the ribosome. This is possible in theory, and some have suggested that present day Earth might have a "shadow biosphere" consisting of RNA world cells, but this has never been confirmed. Maybe we can find RNA world cells on Mars instead? There are many other ideas for early life that could perhaps still exist there, though extinct on Earth, including the so called autopoetic cells that replicate just by producing daughter cells with a similar mix of chemicals when they get large, with no genetic code to regulate the process. Unrelated life, perhaps based on some form of XNA (Xeno Nucleic Acid) instead of DNA . This would be the most amazing discovery of all. It would lift biology into a new dimension, show how life can exist based on completely different principles from DNA based life.



There are many alternatives to DNA and RNA. RNA and DNA are both particularly fragile, DNA especially and hard to form naturally, need the environment of the cell or special conditions to keep them stable. RNA is more stable when it is very cold for instance, and ribose in its backbone is stabilized by the presence of borates , one of the points in favour of an origin on Mars. Some of the others are more robust and some think we may have started with a PNA world for instance as it is far more robust than RNA and forms more easily.



Other ideas for early life include TNA world, or a molecule that's a hodgepodge mixing different backbones in the same molecule with non heritable variations in backbone structure (or a whole alphabet soup" of other possible precursors such as HNA, PNA, TNA or GNA - Hextose, Peptide, Therose or Glycol NA).



The interior of a cell is so complex it's been compared to an entire ecosystem. So life based on different principles could be as revolutionary for biology as discovering a coral reef for your first time, when the only ecosystem you knew about before is the African Savannah. I make this analogy here: "Super Positive" Outcomes For Search For Life In Hidden Extra Terrestrial Oceans Of Europa And Enceladus



. This would be the most amazing discovery of all. It would lift biology into a new dimension, show how life can exist based on completely different principles from DNA based life. many alternatives to DNA ribose in its backbone is stabilized by the presence of borates started with a PNA world Other ideas for early life include TNA world, or a molecule that's a hodgepodge mixing different backbones in the same molecule with non heritable variations in backbone structure (or a whole alphabet soup" of other possible precursors such as HNA, PNA, TNA or GNA - Hextose, Peptide, Therose or Glycol NA). The interior of a cell is so complex it's been compared to an entire ecosystem. So life based on different principles could be as revolutionary for biology as discovering a coral reef for your first time, when the only ecosystem you knew about before is the African Savannah. I make this analogy here: "Super Positive" Outcomes For Search For Life In Hidden Extra Terrestrial Oceans Of Europa And Enceladus Life that is based on novel new principle s that we haven't thought of yet. For instance, what if other life doesn't use a helix? Suppose for instance that the life used a sheet like two dimensional structure, planar rather than linear, and replication happened by a second layer forming on top of the original sheet?



Or could it even be a 3D informational polymer? Is there any approach that avoids the need to uncoil to read it? We can do this mechanically through laser scanning, in prototypes for future memory devices, so the idea is not so far fetched as to be totally impossible.



This is just fun speculation at present. But suppose that you are an ET biologist and your life uses 2D sheets to replicate - would you not find the idea of a helical structure that has to uncoil and unzip to replicate implausible and unlikely too?



s that we haven't thought of yet. For instance, what if other life doesn't use a helix? Suppose for instance that the life used a sheet like two dimensional structure, planar rather than linear, and replication happened by a second layer forming on top of the original sheet? Or could it even be a 3D informational polymer? Is there any approach that avoids the need to uncoil to read it? We can do this mechanically through laser scanning, in prototypes for future memory devices, so the idea is not so far fetched as to be totally impossible. This is just fun speculation at present. But suppose that you are an ET biologist and your life uses 2D sheets to replicate - would you not find the idea of a helical structure that has to uncoil and unzip to replicate implausible and unlikely too? Life that has evolved further than Earth life . Mars has had such harsh conditions in the early solar system, alternating ice and more habitable phases. It's also been subject to strong ionizing radiation, extremes of cold, and near vacuum atmosphere. Some think that we have multicellular life on Earth as a result of a snowball Earth phase. If that's true, you could make a case for Mars life to be more highly evolved than Earth life - more complex, more robust cells, with more non redundant nucleotides, and more capabilities than Earth life, maybe even totally novel capabilities never explored here, even if it is just single cell life.



Present day Mars probably only has microbes, or perhaps lichens, if it is fair to make a comparison with similarly harsh environments on Earth. But the harsh environment may mean it evolved further on Mars than on Earth. Or could mean it didn't get as far and is an early form of life. It's hard to say in advance which way this would go



. Mars has had such harsh conditions in the early solar system, alternating ice and more habitable phases. It's also been subject to strong ionizing radiation, extremes of cold, and near vacuum atmosphere. Some think that we have multicellular life on Earth as a result of a snowball Earth phase. If that's true, you could make a case for Mars life to be more highly evolved than Earth life - more complex, more robust cells, with more non redundant nucleotides, and more capabilities than Earth life, maybe even totally novel capabilities never explored here, even if it is just single cell life. Present day Mars probably only has microbes, or perhaps lichens, if it is fair to make a comparison with similarly harsh environments on Earth. But the harsh environment may mean it evolved further on Mars than on Earth. Or could mean it didn't get as far and is an early form of life. It's hard to say in advance which way this would go Life with a capability Earth life doesn't have, e.g. a new form of photosynthesis .



We have three ways of doing photosynthesis on Earth - broadly speaking.



Green sulfur bacteria , which use light to convert sulfides to sulfur , which is then often oxidized to sulfur dioxide

Normal photosynthesis which splits water to make oxygen, also taking up carbon dioxide in the process. (basic equation 6CO 2 + 12 H 2 O → C 6 H 12 O 6 + 6 O 2 + 6 H 2 O where the oxygen atoms in bold are the same ones on both sides of the equation - see Plants don't convert CO 2 into O 2 , and Notes on lamission.edu )

The photosynthesis of the haloarchaea which works similarly to the receptors at the back of our eyes, based on a "proton pump" which moves hydrogen ions across a membrane out of the cell using bacteriorhodopsin similar to the rhodopsin in our eyes, with no byproducts such as sulfur or oxygen, just creates energy directly from the proton gradient.



ET microbes might well use some fourth form of photosynthesis that has never been explored on Earth.



three ways of doing photosynthesis on Earth use light to convert sulfides to sulfur Plants don't convert CO into O , Notes on lamission.edu Life similar to Earth life in most respects , would raise many questions. How has it evolved in such a different environment, since last transfer from Earth, surely at least tens of millions of years ago. How did it get there? We can test the theory of panspermia, find out in practice how easy it is for life to be transferred to another planet.



, would raise many questions. How has it evolved in such a different environment, since last transfer from Earth, surely at least tens of millions of years ago. How did it get there? We can test the theory of panspermia, find out in practice how easy it is for life to be transferred to another planet. No life but with organics, and all the ingredients for life but no life. This may seem boring, but it would tell us a lot about how hard it is for it to evolve on a planet, and about the paths it follows on the way to life. If not life itself, there has to be some complex organic chemistry going on, and cell like structures surely form, as that happens even in short term laboratory experiments. So how far did it get and what exactly happens on a world similar to Earth in many ways (especially in the early solar system), but without life?



Also, on Earth it's impossible to study uninhabited habitats, except for a very short time after a volcanic eruption. Life appears rapidly on any uninhabited habitat here. On Mars, we might have the opportunity to study uninhabited habitats on a planet that hasn't been inhabited for billions of years. This could help us to understand exoplanets and the origin of life and maybe find out that life is harder to evolve than we thought. It can also help to disentangle effects of life and non life processes on Earth.



This may seem boring, but it would tell us a lot about how hard it is for it to evolve on a planet, and about the paths it follows on the way to life. If not life itself, there has to be some complex organic chemistry going on, and cell like structures surely form, as that happens even in short term laboratory experiments. So how far did it get and what exactly happens on a world similar to Earth in many ways (especially in the early solar system), but without life? Also, on Earth it's impossible to study uninhabited habitats, except for a very short time after a volcanic eruption. Life appears rapidly on any uninhabited habitat here. On Mars, we might have the opportunity to study uninhabited habitats on a planet that hasn't been inhabited for billions of years. This could help us to understand exoplanets and the origin of life and maybe find out that life is harder to evolve than we thought. It can also help to disentangle effects of life and non life processes on Earth. Some major unexpected discovery that nobody currently is likely to predict.

It might seem hard to get excited about microbes - but think of them as microbe ETs, and perhaps you may see them in a different light. As minute emissaries from another biological cosmos, tiny beings with a potentially totally different biochemistry.





This next video shows how DNA makes protein. Notice how complex the process is.

It happens in exactly the same way in every cell of every single Earth creature. Imagine what it would be like to find a cell that does it differently?

I've heard it said that the interior of a cell is so complex, with its million different chemicals, and elaborate structures and processes, that to researchers studying how cells work, it seems as complex as an entire ecosystem. So, what about using actual ecosystems as an analogy here?

Imagine that you have been brought up in the African savannah - with its grasses and trees, elephants and antelopes. You've never seen a marsh or a forest, or a beach. All your life you've lived in a hut in the African Savannah, never traveled more than a few miles from your hut, and that's the only thing you've ever known.



Then one day someone takes you to the sea shore, with its fish, shellfish, seaweeds, and sea anemones, and perhaps they take you on a dive to see a coral reef.

A Blue Starfish (Linckia laevigata) resting on hard Acropora coral. Lighthouse, Ribbon Reefs, Great Barrier Reef. Photo by Richard Ling

The interior of a cell of XNA based life could be as different from the interior of a cell of DNA based life as the African Savannah is different from a coral reef. And imagine the new perspectives we might get if we can study it.

The search for life is the main motive for all the missions to Mars to date. Look at how excitedly NASA reports yet another discovery of possible past or present water on Mars. And what a huge anticlimax it would be to get there, find life, it's headline news in all the papers, and then follows the anticlimactic announcement that it was just life that was brought there by the human explorers themselves! Then would follow speculation and questions about whether there was any native Mars life there before the Earth microbes got there, maybe never answered definitively. Or we find evidence that there was some native life that went extinct in the very decade that humans landed there, an ecosystem of many Mars microbes interacting, now gone. Or we find some present day indigenous life, but it is already getting overwhelmed by microbes from Earth, and there follows a rush to try to find it in the many different potential habitats on Mars before it goes extinct.

I think the example of an early form of life is the easiest to use here to show how vulnerable native Mars life could be, potentially. It could be some form of life that was been made extinct on Earth billions of years ago, RNA world life say. It might not last for long after more modern life from Earth gets to Mars.

For more about this see my article Will We Meet ET Microbes On Mars? Why We Should Care Deeply About Them - Like Tigers

So now, what happens if Elon Musk sends 100 colonists to Mars and then the spacecraft crashes? Out of thirteen attempted landings on Mars (now including Schiaperelli) only seven have succeeded, two soft landed but with no significant data returned, and four have crashed.

Schiaperelli crash site on Mars. The lower white dot is thought to be the parachute and the upper dark dot, the crash site for the lander itself. Mars is the toughest place to land in the inner solar system.



Out of thirteen landers that have attempted to land on the surface of Mars itself, only seven have been successful, with one partial success Mars 3. There have been four crashes Successes: Viking 1 and 2, Pathfinder, Phoenix, Spirit, Opportunity, Curiosity.

Crashes: Mars 2, Mars Polar Lander, Deep Space 2 (same mission as MPL but separate landing) and Schiaperelli

Soft landing but no data or hardly any data , Beagle 2 and Mars 3 Since the focus here is on the risk of a crash on the surface, I ignore missions that never got to Mars. Even NASA has had crashes on Mars with its Mars Polar Lander and Deep Space 2 in 1999, which entered the Mars atmosphere independently and both crashed for different reasons. Since then, they have had a string of successes, with Phoenix, Spirit, Opportunity and Curiosity. However, impressive though that is, you can get a string of four successes easily even if the chance was only 50/50 of success each time. The chance of four successes in a row is then 1 in 16, or a 6.25% chance. This could mean that NASA is better at landing on Mars than ESA. But the statistical significance is not quite 2 sigma, not nearly good enough for scientific validation that they are statistically better than ESA and Russia. ESA did everything right, including a radar to measure the distance to the ground. The ESA has many deep space successes: Mars Express, Rosetta, the Philae Lander was a partial success and was attempting something never done before, Ulysses, the Huygens Titan probe, Venus Express. With Curiosity's seven minutes of terror, the mission controllers really didn't know if it would land safely or not. Even Curiosity 2020 is not guaranteed to land successfully. We might have other reasons to suppose it has a good chance of success, but just based on the statistics, the chance of a successful landing could easily be 50/50 or lower. So similarly, if you got four successful missions using the same system as is needed for humans to Mars in a row, which would count as an excellent record for unmanned missions, it would not give much assurance that your chance of success for the next landing is better than 50 / 50. You'd need other reasons for your confidence if you thought a crash was unlikely.



Following a precedent set by Carl Sagan, planetary protection discussions are often based on the idea that the risk of contamination should be less than 1 in 10,000 per mission (ideally of course the risk should be zero but we don't have that capability at present).

Elon Musk himself warns that there is a high risk of death for the first colonists to go to Mars. With his supersonic retropropulsion proposal, his rockets have to streak across the landscape, so close to the surface that they can't land on mountainous areas on Mars. (Robert Manning talks about supersonic retropropulsion and challenges associated with landing large payloads on Mars here). For more about why it is so hard to land there safely, see my Why do Spacecraft crash on Mars?

Debris from Columbia - broken into tiny pieces by the crash. What if this happens on Mars, with the debris spread over the surface? What happens when the global dust storms strike, and particles of dust, small debris and organic materials from the crash get carried throughout Mars?



Microbes would certainly survive such a crash. Indeed hundreds of worms, much more fragile than hardy microbes, survived the Columbia crash.



One of the Caenorhabditis elegans worms, size of a pin head, which survived the Columbia disaster in an experiment held in six canisters, each containing eight petri dishes.

For more about this see my Why Do Spacecraft Like ESA's Schiaperelli Crash On Mars So Easily?

This surely would be the end of any chance of protecting Mars from Earth life. It is something we can never reverse, once there are hardy spores of Earth life in their countless billions scattered in the dust storms on Mars.

Dust storm on Mars shown in right hand image. After a crash of a human occupied spaceship on Mars, numerous hardy microbe spores would be scattered in the dust storm season, every two Earth years. The effects would be irreversible, and we would have to say that it is no longer possible to protect Mars from Earth microbes.



After that, any experiment that finds present day life on Mars would have to start with the assumption that it might be Earth life introduced as a result of the crash.

NASA's planetary protection office agrees, but say that their job is to work out if the planet can be protected in the case of a successful human landing. So, they don't consider crashes of human occupied ships in their assessments. That is for NASA to look at, at a later stage. Also, they no longer aim for reversible biological exploration of Mars in the case of a human landing.

In their list of knowledge gaps for human extraterrestrial missions, they cover such things as leaks of microbes from spacesuits in EVA, transport of microbes in the dust storms. But there is no mention at all of the effects of a crash of a human occupied spaceship anywhere in the list. They have to assume a 100% success rate for humans landing on Mars as without that assumption they would not be able to recommend any measures that could protect Mars from Earth life, even temporarily.

Their approach is that we will have a small precious window to find out as much as we can about Mars before humans introduce Earth life there by landing on the surface. Emily Lakdawalla, planetary geologist who often reports for the Planetary Society, expresses a similar sentiment in this article

"NASA recognizes that the potential for contamination is a problem, so there is a Planetary Protection Office that is specifically charged with overseeing how missions avoid contaminating Mars with Earth biota. There are two main approaches. One approach is to sterilize the heck out of anything that will actually be touching Mars. That's why Curiosity's wheels were specially wrapped throughout its final assembly, and why it was such a scandal that the drill bits were handled after sterilization. The other approach is to avoid landing in any location where you might encounter -- or accidentally create, should you crash -- a present-day habitable environment where Earth microbes could thrive. For instance, current rules prohibit NASA from targeting a mission containing a hot radioisotope thermoelectric generator (such as Mars 2020) anywhere near a place where a failed landing might place that generator close enough to subsurface ice that the heat of the decaying plutonium could melt it.



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



"This is one of many reasons I'm glad that The Planetary Society is advocating an orbit-first approach to human exploration. If we keep our filthy meatbag bodies in space and tele-operate sterile robots on the surface, we'll avoid irreversible contamination of Mars -- and obfuscation of the answer to the question of whether we're alone in the solar system -- for a little while longer. Maybe just long enough for robots to taste Martian water or discover Martian life."

Cassie Conley has also said she thinks Elon Musks' ideas have planetary protection issues, in an interview just before his big announcement here: Cassie Conley. Going to Mars Could Mess Up the Hunt for Alien Life

There are no detailed guidelines yet for humans to Mars. These would be made by the international COSPAR committee which meets every two years, and all of their discussions to date have ended without any firm recommendations, saying that more information is needed.

I think however that the idea to exploit a brief window of opportunity of a few years before the first human landings or colonization attempts is just not good enough. We simply shouldn't risk destroying such a precious opportunity to make scientific discoveries, on the basis of ignorance.

Here is a quote from When Biospheres Collide

"One of the most reliable ways to reduce the risk of forward contamination during visits to extraterrestrial bodies is to make those visits only with robotic spacecraft. Sending a person to Mars would be, for some observers, more exciting. .... But in the view of much of the space science community, robotic missions are the way to accomplish the maximum amount of scientific inquiry since valuable fuel and shipboard power do not have to be expended ... to keep a human crew alive and healthy. And very important to planetary protection goals, robotic craft can be thoroughly sterilized, while humans cannot. Such a difference can be critical in protecting sensitive targets, such as the special regions of Mars, from forward contamination.



"Perhaps a change in the public's perspective as to just what today's robotic missions really are would be helpful in deciding what types of missions are important to implement. .... The spacecraft instruments, in other words, are becoming more like collective sense organs for humankind. Thus, according to Johnson, when NASA conducts it's so-called robotic missions, people all around the world are really "all standing on the bridge of Starship Enterprise". The question must thus be asked, when, if ever, is it necessary for the good of humankind to send people rather than increasingly sophisticated robots to explore other worlds"

For all we know at present, we might have to travel light years to other star systems to find another planet like Mars to study in its original state without Earth microbes, if we can find one at all. Look at all the mistakes we have made in the past - extinct dodos and passenger pigeons, introducing rabbits to Australia in order to make settlers "feel at home", also introducing feral cats, rats, and making many species extinct, through ignorance of the consequences of our actions. Right now species in the Amazon rainforest are becoming extinct before we know what we have lost.

Martha, last of the passenger pigeons, which once formed huge flocks, and with a population of three to five billion, may have been the most numerous birds on the Earth before they became extinct. Their accidental extinction was one of mankind's many mistakes, and drew attention to the possibility of making even a numerous species extinct.



We haven't got any experience of introducing life to other planets, and so don't have object lessons like this to warn us of what might happen. Science fiction movies like Star Trek may give the impression that we can land humans on any planet in the galaxy, and the microbes they bring with them will have no consequences on the local ecology. However, these are the product of script writers' imaginations, by writers who themselves have no experience of what would actually happen in that situation, and are not predictions of what would happen in practice.

We have made many mistakes already on Earth. Introducing Earth microbes to Mars could easily turn out to be one of our worst ones ever.

I think we need a positive version of the precautionary principle, something like this (I'm no lawyer, I've just taken the phrasing of the Wingspread conference on the precautionary principle, 1998 and changed harmful to "superpositive" and made other similar changes):

"We believe that human activities have potential to lead to discoveries of such positive value, "superpositive outcomes" that new principles for conducting human activities are necessary to ensure that this potential is not destroyed.



"While we realize that the future can't be predicted, people must proceed more carefully than has been the case in recent history. Corporations, government entities, organizations, communities, scientists and other individuals must adopt a precautionary approach to all human endeavors.



"Therefore, it is necessary to implement the Precautionary Principle for superpositive outcomes: When an activity may lead to a superpositive outcome, precautionary measures should be taken to keep this possibility open even if some cause and effect relationships are not fully established scientifically.



"In this context the proponent of an activity, rather than the public, should bear the burden of proof.



"The process of applying the Precautionary Principle must be open, informed and democratic and must include potentially affected parties. It must also involve an examination of the full range of alternatives, including no action."

This could also be applied to other superpositive outcomes such as potential for new medicines and knowledge from tropical jungles. We have no idea what knowledge has already been lost through deforestation and extinction of species that scientists have never had an opportunity to study.

However, I think it applies in an especially overwhelming way to this potential of discovery of novel lifeforms on other planets.

So in this case, for Mars, we do not know what the chance is of a superpositive outcome, such as discovery of a novel exobiology. It is possible that Mars is so unique that we would have to travel to a planet around another star to make the same or similar discoveries there. Indeed, there might also be nothing like it for tens or hundreds of light years in all directions (e.g. if the discovery is related to unique conditions that prevailed in the nebula that gave birth to our solar system).

There is no way to prove that this is the case, of course. But we shouldn't just proceed on a basis of not knowing what the risks are.

Advocates of colonization of Mars project a sense of urgency, that we have to send humans to Mars as quickly as possible to protect our species. Of course their impatience is understandable, as this is something that they have hoped for, for decades. But there is no urgency to send humans there. We are amongst the least endangered of all higher animals on Earth. We could survive events that made the dinosaurs extinct with our mammalian physiology, our omnivore capability to survive on a diverse range of foodstuffs, and the simplest of technology such as ability to make clothes, and boats, to use simple tools, and to cultivate plants, farm animals and fish. We can take our time, and it's not a race to see who gets there first. I'll go into this in detail in Wait, Let's Not Rush To Be Multiplanetary Or Interstellar

The opinion of experts on whether there are habitats for life on Mars and whether there is present day indigenous life there spans the entire range from 0% to 100%. Views on the possibility of present day life on or near the surface.

I argue that it shouldn't be up to astrobiologists to prove that introduced Earth microbes will impact on Mars based just on what we know so far at the time of a human landing attempt. That is obviously impossible to do when we haven't yet sent a rover to examine any of the possible habitats on the ground, and especially if the lions share of funding is used to establish humans on the Mars surface rather than to explore the planet in a biologically reversible way first.

Zubrin has argued that because of meteorite transfer, life on Mars is so similar to Earth life that introducing Earth microbes will have no effect on it. Alberto Fairén and Dirk Schulze-Makuch also suggested that we no longer need to protect Mars, using Zubrin's meteorite transfer argument essentially, in "The Over Protection of Mars". This was rebutted in a follow up article "Appropriate Protection of Mars", in Nature 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,

If Mars and Earth were as similar as this at a microbial level, it would be so remarkable that I think most astrobiologists would want to study the situation on Mars to find out how this happened, before confusing it by introducing more Earth life. The most recent time that Earth microbes could get to Mars is perhaps at the time of the impact that formed the Chicxulub crater, 66 million years ago, and a more likely time for it to happen is in the early solar system, over three billion years ago, soon after formation of the Moon. Also, most Earth lifeforms, including lichens, and many microbes able to survive on Mars, would not be able to make the journey. How likely is it that both planets have the same microbes, after millions, or even billions of years of separate evolution in such different conditions as Earth and Mars, and with only some of the species shared via meteorite impacts, if any? I cover this later in How a human spaceship could bring microbes to Mars - Zubrin's arguments examined

If we have a precautionary principle for super positive outcomes, it is then up to Zubrin and Dirk Schulze-Makuch et al to prove this hypothesis, and not up to the astrobiologists who think we should protect Mars to disprove it. To establish either view is clearly impossible when we haven't yet had an opportunity to do the most basic of preliminary biological surveys of Mars.

So it is a similar situation to the precautionary principle, but in a positive sense. And just as for the precautionary principle, we have to consider the full range of alternatives, including no action, which in this case means that we should consider not sending humans to the Mars surface.

Instead of sending humans as rapidly as possible to Mars, the place in the inner solar system most vulnerable to our microbes, let's send humans back to the Moon.The Moon is the safest place to explore, for its own sake, as a gateway to our solar system. We can have lifeboats there, fueled and with provisions for the crew for two days, ready to take everyone back to Earth in an emergency.





Coast Guard Lifeboat practicing in the big surf just outside and south of the Morro Bay harbor mouth, California. Photo © 2012 “Mike” Michael L. Baird

We can equip a habitat on the Moon with lifeboats for the entire crew, supplied with provisions for two days, to get back to Earth in an emergency.



For a typical Hohmann transfer orbit, the crew are on their own, even one hour after their spaceship sets off for Mars. It won't have enough delta v to reverse course and return to Earth at that point, and there is no other way to get the crew back quickly with present day technology either. They would have to come back via Mars.



This makes the Moon far far safer than Mars for a human crew in the near future.

For that reason, though I'd dearly love to see humans orbit Mars, I think the time isn't right for it yet. We need to do multi-year explorations closer to home before we know that we have the technology and that it's reliable. The ISS is not at this stage of readiness because it is designed for LEO rather than interplanetary missions and it needs to be replenished every few months. The ISS has also had issues with its life support system in the past, which were not serious mainly because it was easy to resupply it from Earth with emergency oxygen.

Getting the mass there is not the main problem; keeping the crew alive is. Nowadays we can keep humans alive in submarines for years on end, if necessary, only resurfacing to take on food, but they are nuclear reactor powered and work by pumping seawater on board and turning it to fresh water and oxygen.

We need a similar level of reliability to get to Mars, but it has to be tested in space, not on Earth, in several shakeout cruises. Unlike nuclear submarines, there won't be any option for the crew to surface in an emergency. They are committed to the vacuum of space surrounding them for two years or more (or 500 days for the shorter round trip via Venus after Mars).

This I think is just not something we can do safely at our present stage of technology. It is probably within reach in a decade or two, but we aren't there quite yet. We have to proceed more slowly. And the Moon is the obvious target here.

Imagine if the early Antarctic explorers had been content to just set foot on the continent and then said "Been there, done that, let's find somewhere else to explore". That's what it is like to go to the Moon in the 1960s through to the 1970s, and then never go back again.

The Moon is both far more resource rich, and far more interesting than anyone realized just a decade ago, with ice at the poles, possibly large quantities of precious metals like platinum from iron meteorite impacts, possibly vast caves below the surface, so large that you can fit the city of Philadelphia inside with plenty of room to spare, and many mysteries to solve. It must have meteorite fragments from the inner solar system, from Earth, Venus, Mars, but unaltered by any geological processes, just sitting there buried in the ice at the poles for billions of years. There is much there that is unknown and to discover, and impossible or hard to detect from orbit (for more about this see science surprises).

Yet, Mars looks so much more habitable than the Moon in the photographs which are digitally enhanced to increase the amount of blue, and to brighten them, to make it easier for geologists to identify the rocks. These press photos are often so transformed the skies are blue rather than the natural grayish brown. I think this is part of the reason why so many people are keen to go there, that it looks so Earth-like in the press photos.

This is a colour enhanced Mars image as you would see it in most press photos - enhanced for the purposes of geologists:

This is what Mars would look like to a typical smartphone camera. It's the raw image from Curiosity (these photos are of Mount Sharp):

Photos from here

Sometimes the sky in press photos of the Mars surface is more of a salmon, peach or pink colour:

This also is colour adjusted. You can tell because the brightest colours on Curiosity are pure white, so it has to be white balanced.

This is one of the raw images used to make it

More raw images used to make the image here - taken with the MAHLI camera at the end of the robotic arm.

This is a recent non colour adjusted image of Mars

As you see the natural sky colour is much more of a brown than a red. It's often described as "butterscotch".

I found, when writing Case for Moon First, that the Moon often beats Mars for in situ resources and habitability comparisons.

So, I wondered, what if we gave the Moon photos blue skies too, like many of the Mars press photos? It's easy to do because the surface is already lit up just as it would be for a sunny day on Earth. We don't need to do anything else, just colour the sky blue instead of black, and it looks Earth-like already. I was amazed at what a difference such a simple change makes to the feel of the scene. You can read it as if illuminated on a sunny day, which is indeed what it was like for the Apollo astronauts.

Original here Apollo 17 at Shorty Crater - blue sky from here

For more examples, see my article: What If The Moon Had Blue Skies? One Small Change To Apollo Photos

These photos are not meant as a suggestion that we terraform the Moon though Gregory Benford and Geoffrey Landis have looked at that possibility too (see the section on terraforming and paraterraforming).

I think the Moon would be a more interesting landscape to human eyes. It's much brighter - which tends to make us feel cheerful. By contrast, the sunlight on Mars at its brightest is half the illumination of Earth, and it's a dull brown in colour with the Mars dust suspended in the air filtering out the blue. Mars never has blue skies except around the sun at sunrise and sunset. Also there is little variation in colour in the landscape to human eyes. It's mainly dull grayish browns, with no blue and none of the bright glints catching the sunlight we have on Earth. I think that any Mars colonists would have a tendency towards depression just because of the rather gloomy sky and dull coloured landscape.

Once we can go to Mars, then we should explore it from orbit. This has no planetary protection issues if done well, and is an exciting mission for the crew. Using telepresence, they can also experience the surface more clearly, with digitally enhanced vision, even blue skies as they explore if they wish.

NASA's planetary protection officer Cassie Conley has talked about the advantages of exploring Mars from orbit first for purposes of planetary protection (see her appearance on David Livingston's the SpaceShow), and she makes strong statements about Elon Musk's rapid colonization plans for Mars as well, in an interview just before his big announcement here: Cassie Conley. Going to Mars Could Mess Up the Hunt for Alien Life

I take this a bit further than this. I don't think we should just delay the landing with orbital missions first, and aim for as much scientific exploration as possible before Mars becomes irreversibly contaminated after a human landing. I think that we should hold off from sending humans to the surface at all, until we have done an adequate exploration first. Then we can make our future decisions based on knowledge rather than conjecture. Our decision can be based on whatever we discover as we explore rather than our present guesses about what we might discover in the future.

As both of them say, and others also, we can do safe exploration of Mars from Earth. We can also explore with humans in Mars orbit, as soon as we have sorted out the safety issues for interplanetary missions without lifeboats to return to Earth in days.

We can explore Mars with robots on the surface controlled from Earth, as we have done so far, and broadband communications would speed up the pace of exploration in this way.

However we can explore Mars much more quickly, with humans in the loop. And you'd use an exciting and spectacular orbit for early stages of telerobotic exploration of Mars, following the HERRO plans. It comes in close to the poles of Mars, swings around over the sunny side in the equatorial regions and then out again close to the other pole, until Mars dwindles into a small distant planet - and does this twice every day. (Technically, it's a sun synchronous Molniya orbit).

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

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



(click to watch on Youtube)

It would be a spectacular orbit and a tremendously interesting and exciting mission to explore Mars this way. The study for HERRO found that a single mission to explore Mars by telepresence from orbit would achieve more science return than three missions by the same number of crew to the surface - which of course would cost vastly more. Here is a powerpoint presentation from the HERRO team, with details of the comparison.

Then, you'd also have broadband streaming from Mars, in wide-field 3D binocular vision. It's amazing what a difference this makes, as I found out when I recently tried out the HT Vive 3D recreation of Apollo 11. We'd have similar 3D virtual reality experience of the Mars surface.

Also, it would actually be a much clearer vision than you'd have from the surface in spacesuits, digitally enhanced to make it easier to distinguish colours (without white balancing the Mars surface is an almost uniform reddish grayish brown to human eyes)|.

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



(click to watch on Youtube)

It's safer too, and comfortable and easy on the crew. No need to suit up. No risk from solar storms - at worst you have to go to a storm shelter in your spaceship, not rush back to your habitat as fast as you can to get out of the storm in time. No risk of falling over and damaging your spacesuit. And when you need to take a break, have your lunch, or whatever, you can just doff the VR set, and then come back, don it again and take it up again where you left off. Indeed you can leave the robot doing some task while you have your lunch or sleep.

Or more likely, you'd control many robots, a bit like the game of civilization. Most of them would be traveling, drilling, conducting experiments etc autonomously, and controlled by teams of researchers back on Earth. The crew in orbit would then step in to take over for any experiments or explorations that can benefit from real time telepresence.

It would be far faster. Curiosity has traveled 15.639 km as of writing this, and traveled 168.45 meters on its drive number 239 which I think is the furthest it's traveled in a day, Lunakhod 2 traveled more than a kilometer a day during it's third lunar day. That's with 1970s technology. A modern rover with modern technology, autonomous collision avoidance etc, could travel many kilometers an hour controlled from orbit, and do thousands of kilometers a year if needed.

Astronauts in orbit could do delicate experiments too requiring fine control. Many modern surgical operations are done via telerobotics with the surgeon in the same room as the patient for safety reasons. However experimentally an operation, the Lindbergh operation, was done on a patient in France by a surgeon in the US with French doctors at hand in case of anything going wrong and it went just fine. There are many other examples of telerobotic surgery over distances of hundreds of kilometers or more since then. We can definitely do delicate experiments on Mars by telerobotics.

There are many other robots we can send to Mars also. They can fly, bounce, go into small caves, go into places we could never explore in person. Any of these could also be controlled via telerobotics from orbit. For more on this see my See my Soaring, Buzzing, Floating, Hopping, Crawling And Inflatable Mars Rovers - Suggestions For UAE Mars Lander.

We don't have to halt or slow down on human exploration to keep Mars protected from Earth microbes. Far from it; we can go somewhere closer to home, and more practical in the near term, the Moon. It's an exciting place to explore, and within our abilities, yet risky. It will stretch our current space capabilities nearly to the limit. We've been to the Moon for short periods only so far, in the early morning of the lunar day. It's far more challenging to stay there for weeks and months on end, safely.

Growing crops in space is likely to be a key to dealing with the high cost of resupply to missions in space, as a way to provide both food, and oxygen for the crew. The Moon has many resources we can use in situ to stay there for longer periods of time, and it's actually quite good for lunar gardening, at least as off world places go. Some of the sites on the Moon may well be the easiest places of all to build a habitable base in the inner solar system.

The peaks of eternal light at the poles have sunlight 24/7 nearly all the year round. They are also only a short distance from what seem to be vast resources of volatiles like water, ammonia, and carbon dioxide.

Then at lower latitudes, the probably vast caves provide radiation protection, protection against micrometeorites, a constant thermal environment actually slightly warmer than the poles, and it turns out that the two weeks long lunar night is something you can work with as a gardener. Many plants can withstand 14 days of darkness with less than 50% reduction in crops if you reduce the temperatures to 2.5 - 3 degrees centigrade. And for plants that do need illumination during the night, the amount of power per colonist is much less than you'd think. With modern techniques and LED lights you only need around 500 kWh per colonist to illuminate all the crops for an entire lunar night. This is an amount well within capabilities of fuel cells, hydrogen storage and advanced forms of batteries etc.

We need to explore the Moon first, probably robotically, before setting up a human base there. Robots are the easiest way to find the best location, and to prepare the habitats for humans. That will also give us practical experience in operating remote robots from Earth much closer and easier to control than the ones on Mars. That may help with Mars exploration too, once we have humans in orbit there, or broadband communications from Earth.

For details, see my An astronaut gardener on the Moon - summits of sunlight and vast lunar caves in low gravity below, which some sites have linked to as "The Complete Guide to Lunar Gardening" :).

For the resource comparison with Mars, see See The Moon is resource rich and to find out about the science interest of the Moon, see Moon science surprises.

And longer term, let's try not to pin all our hopes for human exploration and perhaps colonization on Mars. The solar system is vast with many other places that may turn out to be far better for us, once we understand it better. These include the resources in the near Earth asteroids and the asteroid belt, see my Asteroid Resources Could Create Space Habs For Trillions; Land Area Of A Thousand Earths.

Indeed, if we could use the low impact, closed system, and efficient conveyer based agriculture suggested for space habitats, much of Earth itself is ripe for colonization, including its deserts and the oceans. With that technology, we could feed the entire world from only 2.5% of the Sahara desert. Also our oceans are four times the surface area of the land, in effect giving us four new "ocean world" planets. If we use space habitat technology for the seas as well, we could feed the population of those four extra "ocean world" planets, with four times the population of Earth, from only 0.5% of the Pacific ocean. We are talking here about minimal impact sea steading, in tethered floating sea cities.

These would be floating habitats that rely on just sea water, the air, and minimal imports from the rest of Earth, with no impact on sea life as they wouldn't need to fish and the land area is too small to shade out significant amounts of light if carefully situated. They would be constructed for far less cost than their equivalent in the vacuum of space, and would be far easier to maintain. There's no need to launch everything into orbit to set it up, no need for radiation shielding, and no need to purge the air of the noxious gases that build up inside any human occupied habitat (just open windows). Also there is no need to hold in the air against tons per square meter of outwards pressure, or to wear a spacesuit whenever you go outside. It's far easier to do seasteading than any form of space colonization. For more details, and the calculations, see my An astronaut gardener on the Moon - summits of sunlight and vast lunar caves in low gravity again.

In space, we can set up bases and supply stations in places like the moons of Mars or in orbit around Mars, in the Venus clouds, on Jupiter's moon Callisto, on Mercury, which has ice at its poles, and even further afield in the Saturn system or beyond.

All that is possible with no planetary protection issues for most of the places. Venus clouds and Callisto would need preliminary assessment to make sure there are no issues, but are likely to be okay based on the knowledge so far. There are many places in the solar system that we can visit in person, as explorers who love science and see the scientific value of space exploration as paramount. The places we can't explore in person directly in this way can be explored from orbit by telepresence until we have a better idea of what we are dealing with. There will be no shortage of adventures and new horizons in this future.

PRESENT DAY HABITABILITY OF MARS AND WAYS TO DETECT PRESENT DAY LIFE THERE

Some of you may wonder what the fuss is about as you may have heard that the chance of life on or near the Mars surface is remote. After all, that was what most experts thought until the Phoenix lander in 2008. They thought that life on Mars was possible, but only deep down, for instance in geothermal hot spots isolated from the surface, or in a very deep liquid water layer (the hydrosphere) kilometers down below the frozen surface (the cryosphere).

But the situation has changed a lot since then. So here is an update on what has changed in the last eight years.

Experts still agree that the surface is in a near vacuum and that fresh water exposed to the surface will evaporate rapidly and can't persist in present day Mars conditions. But they have found many ways that various forms of salty water and even trapped fresh water can survive on or near the surface.

This new approach started with the observation of what may be salty droplets that formed on the legs of the Phoenix lander in 2008, gradually grew, sometimes merged, and then fell off. They have also done many Mars simulation experiments and found microbes and lichens that can make use of the 100% humidity of the thin Mars atmosphere at night, with no access to liquid water in any form. In another development, various features were found in the Mars orbiter images that changed as the seasons progressed and were impossible to model using either winds or dry ice processes.

The warm seasonal flows, or "recurrent slope lineae" are just one of many proposed types of habitat for life on the Mars surface. I covered the literature in my detailed survey article Are There Habitats For Life On Mars? - Salty Seeps, Clear Ice Greenhouses, Ice Fumaroles, Dune Bioreactors

There's an almost bewildering variety of suggestions for habitats on Mars for life now. The main surface or near surface ones are (these links take you to the online version of the booklet)

Most of those habitats are either above the permafrost layer or at most a few centimeters below it (the permafrost layer is typically 2 cms below the surface of the Mars regolith or less).

They are all almost impossible to detect from orbit, as they are covered by a few mms of the regolith, or lie beneath layers of ice, and most are also very small in physical extent. The only way we know to explore most of them and in many cases the only way to know for sure even if they exist, is with surface exploration missions, with landers or rovers.

That should be no surprise, because Mars is so cold and dry. It was probably as habitable as Earth originally, but after it lost most of its water, ice and atmosphere, the most habitable places now are like the Atacama desert and the dry valleys in Antarctica. They are cold, and dry, and any life is likely to be so slow growing and sparse that it has no noticeable effect on the atmosphere. Yet, if life did once get established on Mars, it may still be there.

It's rather like the future for Earth itself, which may became as uninhabitable as Mars, hundreds of millions of years in the future (unless some civilization either moves the Earth or shades it from the sun with vast thin film shades). It's likely to get too hot rather than too cold in our case. If so, the chances are that some small remnants of the formerly abundant life would survive long after most other species have gone extinct.

As Nilton Renno said, about his discovery of the possibility of droplets of water on salt ice interfaces on Mars,a droplet of water is like a swimming pool for a bacteria. Relicts of formerly abundant life would be no less interesting for being sparse and hard to detect. For more about this, see my article Why Mars Surface Life May Leave No Traces In Its Atmosphere: Our Rovers May Need To Go Up Close To See It

I think one of the most striking of these suggested habitats for planetary protection, though less well known, are the "flow like features" in Richardson crater near the south pole, as these suggest the possibility of fresh liquid water on Mars trapped below ice. The conclusions of Möhlmann's model are clear - if Mars does have clear blue ice as in Antarctica, then it should also have layers of pure fresh water trapped 10 - 20 cms below the surface, in conditions with surface temperatures as low as -56 C.

If so this may explain seasonal features found in Richardson crater. See my Does Ice Act As Greenhouse On Mars - Fresh Liquid Water Habitats In Spring 10-20 Cms Below Polar Ice?

Then the methane plumes, if they are signs of life, surely must indicate abundant life in more habitable conditions, deep down, with some communication with the surface to let the gas escape. That would suggest of course that they could potentially be vulnerable to contamination by Earth microbes from the surface in the opposite direction. The plumes could also be caused by the inorganic process of serpentization. They may also be due the release of methane clathrates formed on early Mars by either organic or inorganic processes.

There's a wide variety of views on the topic of whether any of these potential habitats are in fact habitable by Earth life. If they exist, they may also be either too salty or too cold for life. Also some of the habitats that work in Mars simulation chambers and theoretical models of the surface may just not exist on Mars, as they depend on conditions we can't know about.

As an example, the fresh water model for the flow like features in Richardson crater depends on clear ice like the blue ice of Antarctica to act as a greenhouse to warm the ice to melting point half a meter below the surface. If similar semitransparent ice exists on Mars, the models show that there will be trapped layers of liquid water in the ice at certain times of the year, but we just don't know if Mars ice forms in transparent layers like that or not.

If these habitats do exist, again we have no idea whether they are inhabited by any form of indigenous life.

Views on this range from almost impossible to very likely, see Views on the possibility of present day life on or near the surface, and for the idea that some of these may be inhabitable but uninhabited, see Uninhabited habitats.

If these habitats do exist and are habitable, there are many Earth microbes which have been shown to be able to survive in Mars simulation conditions, and so could potentially survive there, contaminate them and make it difficult or impossible to study them to find out what was there originally.

Researchers at DLR (German equivalent of NASA) testing lichens in Mars simulation experiments. They showed that some Earth life (lichens and strains of chrooccocidiopsis, a green algae) can survive Mars surface conditions and photosynthesize and metabolize, slowly, in absence of any water at all. They could make use of the humidity of the Mars atmosphere. Though the absolute humidity is low, the relative humidity at night reaches 100% because of the large day / night swings in atmospheric pressure and temperature.

Here is a list of some of them, for the cites see my Candidate lifeforms for Mars in my Places on Mars to Look for Microbes, Lichens, ...:

Chroococcidiopsis - UV and radioresistant, and can form a single species ecosystem. It needs no other forms of life, and only requires CO 2 , sunlight and trace elements to survive.

- UV and radioresistant, and can form a single species ecosystem. It needs no other forms of life, and only requires CO , 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

- 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 CO 2 dominated atmosphere as for Mars.

extracted from permafrost layers on Earth which are able to grow in Mars simulation chambers in conditions of low atmospheric pressure, low temperature and CO 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.

- 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, Halorubrum str. BV (Proteobacteria) could use the CO with a water potential of −39.6 MPa

(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, Halorubrum 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.

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.

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 [200] - only require CO 2 , hydrogen and trace elements. The hydrogen could come from geothermal sources, volcanic action or action of water on basalt.

[200] - only require CO , 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.

Most of these candidates, apart from the lichens, are single cell microbes (or microbial films). The closest Mars analogue habitats on Earth such as the hyper arid core of the Atacama desert are inhabited by microbes, with no multicellular life. So even if multicellular life evolved on Mars, it seems that most life on Mars is likely to be microbial.

The astrobiologists have invented many ingenious instruments we can use to search for life on Mars. We don't need to send humans there. We haven't sent a single life detection instrument to Mars since the Viking landers in the 1970s. Many of these tests are exquisitely sensitive, some can detect a single molecule in a sample, or just a few cells.

The main approaches are

Many of these instruments are small, just a few cms in size, and requiring less than a watt of power, "labs on a chip" some of them already tested and space hardened. Yet none have flown yet. One of them, the Life Marker Chip, polyclonal antibodies experiment was originally included in the payload for ExoMars (more about it here) but was descoped. Before that, Urey was going to fly on ExoMars until NASA pulled out of the partnership.

MOMA will fly on ExoMars, with its ability to detect chiral compounds. Both ExoMars and Curiosity will be capable of Raman spectroscopy. But most of these instruments are not yet included in any mission payloads so we will need to wait a while before we get any results from them.

And, no, we don't need humans to drill. Indeed humans in spacesuits are clumsy at that as we found out with Apollo, and they can't use water as a lubricant. ExoMars will be able to drill down two meters, and the Insight lander was going to drill three to five meters.

The main technology used, the robotic self hammering mole, has potential to drill much deeper than either of those, and certainly to the ten meters depth needed to find organics not degraded by cosmic radiation and solar storms. These moles may eventually drill for tens and hundreds of meters, even for kilometers in Mars conditions at ten to twenty meters a day. Honeybee robotics say that a related technology, their inchworm mole will be capable of drilling up to tens of kilometers through soil, ice and rock without need for a tether and then return to the surface.

For more on this: Will NASA's Sample Return Answer Mars Life Questions? Need For Comparison With In Situ Search

Usually Moon first books, such as The Value of the Moon, Moonrush, and The Moon: Resources, Future Development and Settlement argue that it has material resources that could be exported to LEO, or to Earth, that it has more potential than Mars for commerce, or tourism, that it has volatiles and other resources which can be used in situ to support humans there, and that it is a far safer destination for humans than Mars in the near term.

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. The ESA's 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; a village resulting from co-operation of many nations, rather like the ISS, involving astronauts, Russian cosmonauts, maybe even Chinese taikonauts, and private space as well.

Moon firsters also highlight the science value of the Moon and the many mysteries about it still to be solved. This book covers all those things, but it has an extra message about Mars as well, especially addressed to all of you who love science, such as President Obama. The Moon is part of a larger scale vision about how to explore our solar system in a scientifically responsible way.

This book's strongest message is that if we rush humans to the Mars surface as fast as possible, it is going to get in the way of exobiology - the search for biology based on different principles from Earth life. This search is one of our main science objectives for Mars, and has the potential to lead to the most significant discoveries in biology of the twenty first century. If you love science, you won't want to destroy this chance by rushing to land humans there as fast as possible.

Carl Sagan with a model of the Viking lander, so far the only biological expedition to other planets in our solar system. The two Viking landers in the 1970s were the first and also the last spacecraft to search for extant life directly on Mars. All our rovers and orbiters since then have searched indirectly for conditions habitable for life and in a limited way for organics and trace gases. These could be caused by life, or by inorganic processes (for instance, the organics discovered by Curiosity most likely came from meteorites). Our biological exploration of Mars needs to resume, but we have to do it with sterile rovers or we risk making the anticlimactic discovery of life that we brought ourselves.

It's not us that are the problem, but the microbes that accompany us, trillions of them, in thousands of species, some of which may be able to survive on Mars. Sadly, it would kill us to attempt to remove them from our bodies.

The problem with introducing Earth life to Mars after a human landing or crash is that it is irreversible. There is no way to remove the long lived hardy microbial spores from the planet once scattered in the global dust storms. If any of them encounter habitats they can reproduce in, this would be an irreversible change to Mars for us, for our descendants, and for all future civilizations in our solar system.

New discoveries over the last eight years suggest that such habitats may well exist on Mars, bringing these concerns into sharp relief. (See Present day habitability of Mars and ways to detect present day life there below). If later on, we find that we've made a huge mistake by bringing these microbes to Mars, there will be nothing we can do about it.

This argument has less force for those who think pure science is of only secondary importance compared to colonization by humans. If that describes you, I suggest that you give some thought to the many discoveries in medicine, agriculture, and indeed even in materials science and other areas of industry, that depend on deep knowledge of biology. How might those be impacted (in a positive way) if we understood biology better than we do now, and have examples of life based on different principles from terrestrial life? Perhaps that may help you to relate to the motivation for this book.

There is the safety issue as well. Traveling even to Mars orbit (which has no planetary protection issues if done carefully) may be a step too far. It is like setting out on a two year voyage with no lifeboats, in an ocean so dangerous that you can't survive for more than a minute or two of immersion in the sea without a lifeboat.

Going to the Moon is like setting out on a voyage in equally dangerous seas, but with lifeboats able to get your entire crew back to safety within two days in an emergency. It's going to stretch our capabilities almost to the limit to stay on the Moon through the day night cycle of an entire lunar month. We don't need the extra challenges of an interplanetary mission yet. Apollo 13 could circle around the Moon after its oxygen tank explosion, and return to Earth in a few days. A crew on a Mars expedition which encounters a problem just as it leaves Earth would have to last for around two years before they can come back to Earth in a similar fashion via Mars. (Reduced to 500 days if they can do an extra Venus flyby on the way back)

Jack Swigert (right) showing the apparatus the crew of Apollo 13 got together, with instructions from Earth. They had to fit a "square peg into a round hole", to connect the cube shaped command module lithium hydroxide canisters to the cylindrical lunar module sockets in order to scrub the air of CO 2 . It was a fine display of MacGyver style improvisation even using duct tape to complete the job. Oxygen was not a problem as the lunar module had plenty, enough to repressurize it after each EVA. But carbon dioxide poisoning was a real risk and they needed to use the command module canisters to scrub the air, or they'd have passed out. In this way they were able to use the lunar and command module systems together as a "lifeboat" to survive the journey around the Moon and back to Earth.

This shows the path taken by Apollo 13. Although the accident happened only fifty six hours into their flight, the safest way to get back was via the Moon, and they got back three and a half days after the accident.



If an Apollo 13 style accident happened to a human occupied spacecraft on the way to Mars, even if it happened just after the crew left Earth, they would not have enough delta v rocket power to get back to Earth. Rather, like Apollo 13, they would have to go all the way to Mars and back before they could be rescued. However this time it would be a multi-year journey to get back.



For this reason spacecraft systems for multi-year journeys must be supremely reliable and tested. I don't think we are likely to reach that level of confidence until we have had several such missions closer to Earth, on the Moon or in the Earth Moon system (for instance, exploring the far side of the Moon remotely from the L2 position). They need to be missions able to function without resupply of essential supplies from Earth, which would also be necessary to reduce costs. The ISS doesn't count, because it is designed for LEO rather than for multi-year interplanetary missions, and has to be resupplied every few months from Earth.



The Moon is far safer, as all the crew can be supplied with lifeboats with provisions sufficient to get them back to Earth safely within two days. It's still a major challenge that will stretch our capabilities almost to the limit. The later Apollo missions made it seem almost easy, but it was far from it.

Let's start with the Moon for both safety and planetary protection reasons. It's turned out to be far more interesting than previously expected, with many science surprises and surely many more to come. It's also resource rich, indeed in one comparison after another, you may be surprised to find out that it comes out better than Mars for in situ resources.

Then longer term, let's stay in orbit around Mars for now, visit Callisto, the clouds of Venus in airships and floating habitats, Mercury, the asteroids - and further afield. But if you land humans on Mars, that has a potential for an irreversible impact on discoveries in exobiology not just for us, but for all future civilizations on our planet and in our solar system. If you love science, you may well agree that we just must not do this until we have a better understanding of the possible impacts of our actions. It's what I've called a "superpositive outcome".

Also, protection of our beautiful Earth, so hospitable to humans, should be a top priority. I know this will be controversial with many saying we have to go multiplanetary to survive. But we face no immediate natural threats of human extinction. A creature as versatile and adaptable as us with minimal technology could survive any of the natural disasters Earth has been through for billions of years, see 90% of species extinct converts to zero probability of humans extinct. As for the possibilities of making ourselves extinct by our own actions, those could as easily be a consequence of a rush to colonize as averted by them, so what matters is not so much whether we colonize as how we do it. If we have protecting and cherishing Earth as our top priority, I think that will lead to a healthier approach to space settlement. I cover this in the section: Wait, Let's Not Rush To Be Multiplanetary Or Interstellar

I hope this book will stimulate discussion of these ideas.

THE MOON IS DANGEROUS ENOUGH AT THIS STAGE, HARDLY EXPLORED BY HUMANS, WILL STRETCH OUR CAPABILITIES TO THE LIMIT

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The Moon is hardly explored by humans. So far we've only explored locations close to its equator, on the near side. Also we've only ever visited it in early morning of the lunar day - the safest time for humans to be there. The longest visit was for three days and only one party (Apollo 17) had a geologist on board. Every EVA there was dangerous, and we haven't been back there since the 1970s. Since then, we have only shuttled back and forth between Earth and LEO for several decades.

To take the next step, to last out on the surface of the Moon for an entire lunar month, through the heat of the two weeks long lunar day and the darkness and cold of the lunar night, is a bit like overwintering in Antarctica for the first explorers, after they proved that they can land on the continent and walk around for a day or two there. Expeditions to the lunar poles don't have this issue as they have sunlight nearly 24/7 but they have many other challenges of their own. The Moon is not at all well known on the surface at present and we can expect many surprises and difficulties to overcome.

So the Moon is a more natural starting point, I'd love to see humans to Mars orbit, and if it is done carefully, this has no planetary protection issues, as we'll see in this booklet. But we should start closer to Earth first. The secret to success for Apollo 11 was a step by step approach, starting with orbital tests around Earth, the first orbit of the Moon with Apollo 8, and so on. A similar step by step approach ending in a mission to Mars orbit would start with two year missions closer to Earth, before we try the long mission to Mars without lifeboats. We would then explore the surface from orbit via telepresence, just as we often explore the sea bed, ship wrecks, etc.



PLANETARY PROTECTION IS COMMON SENSE - LET'S LOOK FIRST BEFORE WE LEAP

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There are places on Earth we don't go to because they are unsafe, e.g. into the crater of an active volcano. We send expendable robots instead.

There are other places tourists and explorers can't visit because we would harm what's there, e.g. ancient cave paintings where just the human breath is enough to damage them, as we discovered with the Lascaux paintings. New discoveries of prehistoric cave art are immediately set off limit to all except a few scientific researcher. This happened for instance for these recently discovered 14,500 year old cave etchings in Iberia.

14,500 year old art found inside an Iberian cave. As soon as new cave art like this is discovered, the cave is made off limits to all except a few experts ,because humans can damage the paintings and etchings just by breathing inside the cave.

And though they are rare on Earth, there are places here too that we don't go to, to avoid contaminating them with microbes. We haven't sent a submarine into Lake Vostok.

Lake Vostok in Antarctica, a deep subsurface lake isolated from the surface for perhaps 500,000 years. The Russians drilled nearly all the way through but stopped. They then used a method of drilling that made sure that the water rushed upwards from the lake with no risk of contaminating it with surface life. This is perhaps the closest we have to planetary protection on Earth.

Even robots are hard to sterilize sufficiently to explore it, so they haven't yet sent a robotic submarine into it either. They have only drilled in such a way as to cause a geyser which they sampled before it rapidly froze over, and there are questions about whether what they sampled adequately represents what is in the subsurface lake or is contaminated by surface life.

Visitors to Antarctica also have to clean their boots to avoid introducing novel microbes and microfauna and flora to the Antarctic soil. Sadly, cleaning our boots is not a sufficiently stringent measure to protect Mars from our microbes, as we will see.

I suggest in this book that just as with lake Vostok in Antarctica, and with even stronger motivation, there are places in our solar system that should be similarly off limits to humans at least until we understand them better. Mars, Europa and Enceladus are the three top places in the solar system with planetary protection issues.

Once it is safe to travel on interplanetary missions, there are many other challenges solar system wide. There are no planetary protection issues for the Moon, Callisto (probably), Mercury, Venus clouds (probably), and most asteroids and the moons of Mars. Let's focus on those first. Let's not rush humans as quickly as possible to the one place in the inner solar system where their microbes can cause most damage. On behalf of those who love science and think that new discoveries in biology have value for our future, please, let's look first before we "Leap to Mars"!

Originally published on my Science20 blog here: Does Elon Musk's Plan Violate The Outer Space Treaty - Planetary Protection For Mars After Human Crashes

This is a news story that broke recently, on the idea that Elon Musk's plans would violate the Outer Space Treaty. The articles I've read so far focus on property rights and the provisions in the OST that rule out ownership of territory. But that can be fixed with future legislation, especially since it's not really the land but the habitats that are of most value, and ownership of those is already covered in the OST . So far none of them have mentioned by far the toughest legal and practical obstacle, which is planetary protection of Mars from Earth microbes to preserve its science value for the future of mankind.

That can't be fixed by passing new laws. Elon Musk says the mission would be dangerous, with colonists risking death, especially the first ones. The biggest danger is on landing, and a crash of a human occupied ship on Mars in a Challenger type accident would strew fragments of bodies, food, water, air, and spacecraft over the planet. That would be pretty much the end of any planetary protection of Mars.

The planetary protection requirements are not just a result of decisions by fussy bureaucrats. The ones responsible are concerned astrobiologists, such as Carl Sagan and Joshua Lederberg (nobel prize winning pioneer in microbial genetics), and built up in detail over many discussions by international groups of astrobiologists and other scientists in biannual meetings of COSPAR. Nor is it a minor concern of detail. They are concerned that we could rob ourselves and future generations of discoveries in biology as fundamental as the discovery of the helical structure of DNA or the theory of evolution.

So far every space faring country has taken care to sterilize their spacecraft if necessary and abide by the provisions of the OST as interpreted by the COSPAR meetings and guidelines. Most have signed and ratified the Outer Space Treaty and even the United Arabic Emirates, who haven't ratified it yet, say that they will take care to abide by its provisions if they succeed in their plan to send a mission to Mars. It just makes sense to do so.

Then, Curiosity's "seven minutes of terror" wasn't just hyperbole. There was a real risk that it would crash, especially with such novel technology, with many previous examples of crashes on Mars. This is especially tricky with the Mars atmosphere too thin for a conventional parachute to work by itself - but with the gravity too much for a lunar module type landing. You need to refuel to get back to orbit again.

Elon Musk's idea is to use supersonic retropropulsion. The rocket lands on the Mars surface in reverse. It has to use the atmosphere for aerobraking, and simultaneously fires its rockets to bring it to a standstill on the surface. The atmosphere is only thick enough for this close to the surface, so it skims down to a landing within a few kilometers to the surface - so close that it can't land on mountainous areas of Mars because the air is so thin.

Artist's impression of red dragon doing supersonic retropropulsion over Mars, image SpaceX

The planetary protection office, and COSPAR have discussed human missions to Mars. There is no set out protocol yet, but in their preliminary discussions they suggest human missions confined to a particular area of the surface. They accept that this is an irreversible introduction of Earth microbes to Mars and just aim to limit and delay the impact.

However they do these planetary protection assessments of human missions to Mars based on the assumption of a successful landing on Mars. They don't consider the possibility of a crash as that's left to mission planners at a later stage. Yet, for robotic orbiters Mars is treated as a Category III mission and needs to be sterilized to levels that will make the mission safe in case the orbiter crashes on Mars!

At some point someone has to consider what the effect would be of a human crash on Mars, and once you consider that, and if you assess the planetary protection issues for it, I don't see how anyone could either say that a crash won't happen, or that a crash would be anything short of a total end of protection of the planet. It might not be the planetary protection office that do this, if they continue with this policy of assuming 100% successful landings in their assessments. But someone has to do it.

I think that an orbiter mission for humans on Mars also needs assessment for the possibility of a crash on Mars just as for robotic orbiters. There could be ways to make it safe enough so that the possibility of a crash is for practical purposes non existent.

First, I think flyby missions like Robert Zubrin's Double Athena Flyby could be made sufficiently safe for planetary protection. This is an interesting mission that does two flybys of Mars and in between orbits almost parallel with Mars for half an orbit or one Earth year. The crew are close enough to the surface of Mars for telepresence style telerobotics for of order of hours, for both flybys, and are within close range of the planet for days.

Flybys can be done accurately, we've done multiple flybys with Cassini and other spacecraft. We haven't yet had a crash during a flyby mission. You'd use trajectory biasing, so that the final stage misses Mars, and so that if something goes wrong the human occupied spacecraft also misses Mars, and then do gentle nudges to keep it on target, and months during which you can refine the orbit and make sure you are on target.

I think that an orbital insertion maneuver though could go wrong and lead to humans crashing on Mars as has already happened, with the Mars climate orbiter.

Another type of transfer though is very safe - that's ballistic capture. In this approach, the spacecraft is launched to arrive in a distant orbit around Mars, at just the right speed so that it is captured by Mars as a temporary distant extra minimoon with no need for an insertion burn. The crew then can use ion thrusters to slowly modify their orbit to get close to Earth for telepresence during part of the orbit. Ion thrusters change orbit so slowly, that there's not really any significant risk of them accidentally impacting on Mars. So it's much safer for the crew also, and I think probably has no significant planetary protection risks.

This would need to be looked at carefully, and you need to consider also whether any waste material ejected from the spacecraft could hit Mars, but it does seem you could have human missions to Mars that don't need to be sterilized to the levels needed for robotic orbiters to date, without compromising on planetary protection.

HOW A HUMAN SPACESHIP COULD BRING MICROBES TO MARS - ZUBRIN'S ARGUMENTS EXAMINED

Extremophiles that also live in human habitats and found in spacecraft clean rooms can survive in the suggested habitats on Mars if they exist and many have hardy spores and other dormant states that could be carried in the global dust storms throughout Mars. Humans are not the problem, the microbes that inevitably come with them are. After that, any searches for present day life on Mars would need to have as the default hypothesis that what they find was brought to Mars on that crashed human mission, an enormous impact on scientific exploration of Mars.

It would not be "easy to distinguish" as Zubrin suggests with the analogy of anthrax, as only 100,000 of one trillion microbe species, 0.00001% have had gene sequences published. It's not at all practical to have an "inventory" of every single microbial species on the spaceship.

Also archaea swap DNA fragments very readily via horizontal gene transfer so could do that with life on Mars, if related, by an ancient mechanism that goes back billions of years. If related, even if the common ancestor came from lifeforms that seeded our solar system from another planet around another star at birth via panspermia, then the DNA could get mixed up to the extent it is hard to tell what came from Mars and what from Earth.

But most vulnerable would be some early form of life. There's the shadow biosphere hypothesis for Earth that there might be tiny RNA lifeforms here with no DNA or proteins, so having much smaller cells. None have been found, and if that was what came before modern life, it is probably extinct here, as also all other suggestions for life precursors. They may perhaps still survive on Mars. If so then modern life could make them extinct on Mars just as it did on Earth.

Or the life on Mars could,