Blogs/Robert Walker/What would it take to access the newfound lake on Mars?

Well - here we are talking about ice, so it’s comparatively easy to penetrate, by drilling or melting. Methods are already worked out for Europa. Brian Wilcox is working on a 100% sterile probe to descend into the Europan ocean (https://www.manufacturing.net/news/2017/03/nasa-tests-robotic-ice-tools). It would have vacuum insulation like a thermos flask, a blade that cuts ice chips that the body then melts and analysed. It would be sterilized first by heated to over 900 °F (500 °C) during its cruise to Europa which would not only kills microbes but also decomposes organics that would confuse the results.


 * Vacuum insulated probe for Europa (screenshot from this YouTube video (https://youtu.be/nBzBeYsdNsM)) - it doesn't heat the ice directly. Instead a blade at the tip cuts the ice into chips which the probe then melts and analyses. The probe would be heated to over 900 °F (500 °C) throughout the cruise out to Europa. It uses plutonium 238 for the melting - and so, presumably for its power source too, so there is no problem with batteries vulnerable to heating.


 * He describes it in a paper here (http://ieeexplore.ieee.org/abstract/document/7943863/) (abstract, the paper itself is behind a paywall).

In his abstract he says


 * "A central thesis of this work is that we must start by addressing the Planetary Protection constraints, and not to try to add them on at the end. Specifically, all hardware in the probe would be designed to survive heat sterilization at 500 °C for extended periods, as required to meet the COSPAR 1-in-10,000 probability per mission of biological contamination of the ocean"

The NASA summary says


 * "To ensure no Earth microbes hitched a ride, the probe would heat itself to over 900 degrees Fahrenheit (482 degrees Celsius) during its cruise on a spacecraft. That would kill any residual organisms and decompose complex organic molecules that could affect science results."

He doesn't actually say 100% sterile in the abstract, though the NASA summary implies that it is. Anyway, surely after a three year cruise at a constant temperature of 500 °C, there would be no viable life on it, and organics decomposed too, as this is way above the 300 °C temperatures at which amino acids swiftly decompose.

This is a design for a spacecraft, rather than a completed real world device as yet. But it is surely feasible.

We also have Honeybee Robotics inchworm mole (http://www.lpi.usra.edu/meetings/robomars/pdf/6095.pdf) which 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. But I am not sure how sterilizable it can be.

IS THERE A RISK OF DEPRESSURIZATION?
Since it is part of the question, better answer this. I don’t think there is much risk of it depressurizing. Not at a depth of 1.5 km, and at such low temperatures. When the Russians drilled into lake Vostok then there was an immediate inrush of water from the lake, but it froze rapidly as it rose and only rose a few tens of meters. Agreed, the water may be very salty and so not freeze so easily. But on the other hand the water is already thought to be below -10 °C, and the surface conditions on Mars are extremely cold.

Anyway if we use an ice mole, or inchworm, this risk is completely eliminated as it refills the ice tube behind it as it burrows into the ice so there is no direct connection to the surface. Even if there is a significant amount of overpressure, and the water doesn’t freeze (maybe kept liquid by the salts in it), it can’t reach the surface.

But there is a significant risk of a robotic probe introducing Earth microbes into the lake. If that happened we could have the awful anticlimax that after all our work to try to study Martian life, that we find life there - but only the life we brought there ourselves.

NEED TO PROTECT ANY LIFE IN THE LAKE FROM EARTH MICROBES
The normal planetary protection requirement is that you have to be confident that there is at most a 1 in 10,000 chance of contaminating it per mission. It is the original idea behind the current guidelines for the Viking Mars lander calculations, though since then the requirements have been simplified to “pre-heat sterilization” for Viking on the basis that the unexpectedly harsh environment on Mars is roughly equivalent in its effect to the hours Viking spent in the ovens before it was launched to Mars.

Nobody has yet really worked out what the precautions should be for a probe that directly contacts liquid water on Mars. The usual thing to say is “Viking sterilization or better” but - is this good enough?

Viking was sterilized for a soft landing on a dry surface. It may have had 30 viable cultivable spores on it, which, given that typically only 1% of dormant microbes can be cultivated, could mean up to 3,000 viable non culitvable dormant microbes on launch. Is that good enough to ensure only a 1 in 10,000 chance of contamination if it contacts water directly?

PERSONAL VIEW - SHOULD AIM FOR 100% STERILE - ANALOGY OF A MING VASE
If you value the astrobiological insights from Mars - personally I’d go for less than 1 chance in 10,000 anyway.

I like to use the example of a Ming vase.

Would you hand a valuable Ming vase, say, to an art dealer to inspect if they said


 * "You may have read the news stories about people who lost their precious vases because of my clumsiness. That's true. I handle about a 100 a day and about three times a year I drop the vase and it shatters - but there is only one chance in 10,000 that I'll drop it"

"So it is perfectly okay to give me your precious vase! "*

Or would you look for an art dealer who isn't so clumsy?


 * This Ming vase was sold for over ten million dollars on May 30 2006 (http://www.greatestcollectibles.com/most-expensive-vases/#.WKOSTG-LRQI), making it the most expensive vase at the time. Steve Wynn bought it and donated it to a museum. If you had this vase, would you hand it over to an art dealer who told you he or she had a track record of breaking one vase in every 10,000 they handle?

At the time of Viking we had no choice really. Well, we could have decided not do the mission at all, or we had to accept a small chance of contaminating Mars.

The actual figure of 1 in 10,000 risk of contamination per mission is rather arbitrary and it’s not entirely clear how it was arrived at (are two suggestions, one possibility is that it derives from a “for instance” calculation in a paper by Coleman and Sagan). It has just stuck in absence of any reason to choose any figure over any other one.

However, our capabilities for high temperature electronics have improved immensely since Viking.

It is true that the consumer electronics for normal applications are much more heat sensitive, and that typical modern spaceflight components could not withstand heat sterilization any more. But that is just because they are not selected for heat tolerance.

At the same time we have components that can withstand far higher temperatures than their counterparts could in the 1970s. A modern lander could withstand temperatures of 300 °C if we used high temperature electronics, far higher than for Viking.

So we do have the technological capability to make 100% sterile probes now. Which is why Brian Wilcox’s proposal is realistic. It can be done with mainly off-the-shelf commercial components - just - different ones from the ones normally used for spacecraft, which may cost a little more. Components designed for instance for installation close to the engines of aircraft or for car engines at high temperatures.

Brian Wilcox’s probe is limited in its capabilities communicating with a Europan surface lander which is not 100% sterile in the same way. But the Venus rover team has worked out that we could make an entire planetary rover, with all its components capable of operating at 300 °C using mainly commercial off the shelf components, and suggested this may be of interest to planetary protection.

At that temperature all the amino acids decompose rapidly so it destroys not only life but even the organic chemicals that could confuse searches.

The rover or probe would not need to operate at 300 °C of course. But it could be kept at that temperature throughout the cruise from Earth to Mars. The amino acids are destroyed within time periods of minutes to hours so you can be certain that after six months at 300 °C, it is thoroughly sterilized, not a 1 in 10,000 chance, but complete certainty that it is 100% sterile.

As my personal view then if you want to drill into a subsurface lake and be sure that you don’t contaminate it with Earth microbes it needs to be capable of being 100% sterilized like the Brian Wilcox probe.

Also even RNA and other biological molecules on the probe could confuse the search - and possibly even be incorporated into some alien biochemistry. Or if related, even GTA’s (Gene Transfer Agents), small packages of genetic material, could transfer capabilities to Maritan life even if all the life on the probe is dead. So that’s a major advantage of this approach too, that it removes those as well.

It would still be pre-sterilized like the Viking probes - and it could also be post sterilized with CO2 snow, in order to remove any last traces of organics. The experiments would be the most challenging, but there are many instruments too that can be sterilized to 300 °C, again it is a case of designing the instruments for high temperature sterilization (remember they don’t have to operate at those temperatures, just survive them). Again the Venus rover team found that many instruments could already be included in the rover, often designed “off the shelf” for high temperature commercial applications. It is best if the entire rover can be kept at that temperature during the voyage out.

Another issue might be the parachutes - these might need to be sterilized in other ways, for instance using ionizing radiation - but there is no reason why the whole thing can’t be 100% sterile. Can the instruments the astrobiologists wish to send to Mars be sterilized in this way? If they can’t be heat sterilized, e.g. the media for the microbes to feed on in the Viking labeled release, can they be combined somehow with a heat sterilized rover, but sterilized in some other way?

This would be a major project, but it could be combined with the Venus lander work, and the upside would be enormous, 100% sterile probes and rovers for subglacial lakes in Antarctica, and for all the locations in the solar system where we wish to search for extra terrestrial life. We would then never need to have concerns again about risking introducing Earth life to other places in the solar system in our explorations.

For more on this:

Can we achieve 100% sterile electronics for an Europa, Enceladus, Ceres, or Mars lander? (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_110_1483025424)
 * High temperature sterilization (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_111_1483025424)
 * Multiple methods at once - e.g. 200 °C or higher to sterilize, CO2 snow to remove organics (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_112_1483025424)

and
 * Analogy of a Ming vase - what is an acceptable level of risk for making all the life in Europa's ocean extinct? (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#published_europa_lander_guidelines)

This is a topic on which there are wide ranging debates in the astrobiological literature.

EXAMPLE OF RNA WORLD LIFE TO SHOW HOW VULNERABLE IT COULD POTENTIALLY BE
It’s hard to say how advanced Martian life would be. You can argue both ways. It was as habitable as Earth, probably before Earth. But it soon became a “swan song biosphere” - a world that is almost but not completely dead. How rapidly does life evolve in the harsh conditions of a swan-song biosphere?

If it has continued to evolve rapidly or it was seeded by life from Earth, the life there may be as advanced as Earth life, maybe even more so (if only microbial).

If the life got stuck in an early phase from three billion years ago, and if the structures in ALH84001 are indeed life and we go by the hypothesis that the are tiny RNA world cells - then the life there may be very primitive indeed.

Indeed, one theory is that life on Mars seeded Earth, because its ocean may have formed first. If so, it could be that Mars had a diversity of early life only some of which got to Earth - whatever life was hardy enough to withstand the interplanetary journey on asteroid impact debris. If that was right, Mars could be like a time machine not just back to Early Earth but maybe something more diverse than the earliest life on Earth.

A discovery of, say, RNA world life on Mars might seem academic- but actually - it might be of great financial value, too for its multiple insights into biology, biochemistry, nanoengineering, etc. Such fundamental insights could be far reaching in their impacts, valued far more than a Ming vase, leading to discoveries that lead to whole new multi-billion dollar industries in the future.

TREASURE BEYOND COMPARE - EVEN IN AN ECONOMIC SENSE
To find such life on Mars would be a treasure beyond compare, for biology and possibly also for agriculture, medicine, nanotechnology, industrial enzymes (the market for enzymes derived from study of extremophiles is a bllion dollar industry) - this could be the basis of a multi-billion dollar industry as well.

For more on this see these sections of my online OK to Touch Mars? book (http://robertinventor.com/booklets/If_humans_touch_Mars.htm)

Benefits to humanity from astrobiology (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#astrobiology_benefits)
 * New dimension to biology (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#biology_new_dimension)
 * New biological materials (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#new_biological_materials)
 * Genetic firewall (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#genetic_firewall)
 * Industrial applications of astrobiology already- enzymes from extremophiles (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#industrial_applications_astrobiology)

If we are not careful, we could lose such a treasure, perhaps even before we know it is there.

SCIENTIFIC VALUE AND VULNERABILITY
However whether it has great financial value or not, the scientific understanding that comes from the opportunity to study such a thing in our solar system might well also be priceless, literally.

I like that example of “RNA world” life - life that doesn’t have any DNA or proteins, only RNA, and any enzymes made up of snipped and rejoined fragments of RNA, because it makes it so clear how little we know about what we might lose on Mars in the worst case. Despite what some people might say, we do not know if any Martian microbes would be related to Earth life or not. It is possible to find an independently originated biochemistry there. Astrobiologists when designing instruments they want to send to Mars are careful to design them to be able to detect any concievable biochemistry if possible. They do not assume that it uses DNA for instance.

A discovery of RNA world cells, for instance, could be a discovery that you couldn't replace in any other way, at any price at all. Totally beyond price, of incalculable value for science and understanding of biology, medicine etc. Why do we have to take such a risk? Especially if there is some other way to do it that avoids the risk, even if it is a bit more expensive.

I don't see how it is a justifiable risk myself. How can we take such a risk of losing something as precious as - say - RNA world life that has never evolved to DNA - and perhaps - is still in the pre-Darwinian phase that Carl Woese hypothesized Earth life may have gone through, when there was no interspecies competition, no distinct species as such, just RNA capabilities shared by everything.

CARL WOESE’S “ON THE EVOLUTION OF CELLS
This example is based on a direction suggested by Carl Woese, in a 2002 paper On the evolution of cells (http://www.pnas.org/content/99/13/8742), and followed up in many recent papers on early pre-LUCA life (“Last Universal Common Ancestor).

He proposes that there may not have been a single LUCA. Instead, it may have been a community of "modifiable cells", evolving by sharing new traits widely by massively horizontal (Lamarckian) evolution and working together much like the microbes in a biofilm. This is still a large component of evolution for modern archaea, where both vertical Darwinian evolution and horizontal Lamarckian evolution play major roles.

One hypothesis for the minute cell like structures in the controversial martian meteorite ALH 84001 is that it might be an early form of life of this type, with cells so small because they do not need the complexity of modern Earth life, because they share capabilities with each other and are much simpler lifeforms, with no need for defences and a simpler biochemistry, perhaps based on RNA only and without the enormous ribosomes, that our cells use to make proteins from RNA.

Instead they might have the much smaller ribozymes as enzymes, and they may not use proteins at all. It is possible that such life, if these structures were life, might still be there on Mars, although it is long extinct on Earth as far as we can tell (searches for it as an RNA world "shadow biosphere" (https://aeon.co/essays/does-earth-have-a-shadow-biosphere)have turned up a blank).
 * ONE CONCRETE EXAMPLE - COULD MARS HAVE SZOSTACK LAB TYPE PROTOCELLS OR VERY EARLY CELLS?**

For one concrete example, this is my own suggestion, not seen anyone else make this connection - but perhaps life on Mars resembles the RNA only protocells currently being researched in the Szostack lab ( (https://docs.google.com/document/d/1QJgApnOW88OXgjuC7ktzaYiiE7UQHay2ihBWC9TARKw/edit#bookmark=id.hkr41isakkgy)“On the Origin of Life” (http://molbio.mgh.harvard.edu/szostakweb/publications/Szostak_pdfs/Szostak_2016_MedicinaB.pdf)) (https://docs.google.com/document/d/1QJgApnOW88OXgjuC7ktzaYiiE7UQHay2ihBWC9TARKw/edit#bookmark=id.hkr41isakkgy). These protocells:
 * have no proteins
 * replicate as elongated strands that split when agitated,
 * have RNA, but with a non uniform backbone to the RNA (which actually helps with the primitive form of replication it uses). No DNA
 * use catalysts such as manganese ions to assist replication, and don’t yet have any specific enzymes to speed up replication.

The RNA does not yet have a functional role in these cells but they are hopeful that it will in the future, and that the cells will then be able to evolve to greater complexity by themselves.

So - suppose there is life like that on Mars right now?

We have no idea how fast life typically evolves, how long it takes to get from organic chemistry to a proto-cell, or from a proto-cell to RNA world cells (or whatever comes next) or from RNA world cells to DNA.

Any of those steps might concievably take billions of years. Indeed - one idea for Earth life is that it might have originated around another star that seeded our sun’s birth nebula (along with the other stars in it) - if so it may have taken 5 billion years to evolve as far as the LUCA.

For more on this see these sections of my online OK to Touch Mars? book (http://robertinventor.com/booklets/If_humans_touch_Mars.htm)
 * Half of the pages of the book of evolution have been torn out (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_16_1482841503)
 * Could we peek into these missing pages of the book of evolution on Mars? (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#could_we_peek)
 * ife on Mars dancing to a different tune (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_17_1482841503)
 * Distant cousins with last common ancestor from a planet around another star (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#distant_cousins_around_another_star)
 * How life could transfer between sibling stars in a stellar nursery by "weak transfer" of meteorites (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#stellar_nursery)
 * Infecting an entire star cluster with life from planets from an earlier, perhaps billions of years older star (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#billions_of_years_older_star)
 * Surprising distant cousins (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#distant_cousins)

On such timescales, and with Mars so briefly habitable - it could have pre-LUCA life - and it could even still be at the stage of protocells or autopoetic cells.
 * EARLY LIFE COULD BE EXCEPTIONALLY VULNERABLE TO MODERN EARTH LIFE**

Such would be exceptionally vulnerable to modern Earth life, easily made extinct by whatever processes made it extinct on Earth. After all - wherever we look on Earth - however cold, hot, dry, salt, humid, acid, alkaline, kilometers deep or high in the upper atmosphere - all the life we find is DNA based life.

But this can’t possibly be the first form of life to arise on Earth.

From the *Size Limits of Very Small Microorganisms (1999)* (https://www.nap.edu/read/9638/chapter/2). If you are talking about modern life, then even the smallest cells, the ultramicrobacteria as they are so called, have to be quite large. Every cell has DNA for inheritance, which is unzipped and converted to messenger RNA, and then to proteins, always using the same translation table to convert the RNA chain, three bases at a time, into amino acids. But the main limiting factor in all this is not so much the complex DNA to RNA conversion - but rather, the ribosome which does this translation from RNA to proteins. It is a rather huge molecule made up of a mix of proteins and RNA. One well studied ultramicrobacterium, S. alaskensis, manages just fine with only 200 ribosomes though it can contain up to a maximum of 2000 ribosomes. The smallest spherical cell you can fit all the ribosomes into is about 250± 50 nm in diameter.

There is just no way you can have a cell with 2000 ribosomes 200 nm across with DNA, RNA and all the other interactions in such a cell spontaneously form from pre-biotic chemistry. We can’t even make such a cell from scratch deliberately - before you could get all the chemicals needed together, even if we had a complete specification (which we don’t really, we know how to modify cells, not really to make them from scratch) - they would start reacting and it would destroy itself before our eyes before we could finish its construction.
 * WHY MARS LIFE COULD BECOME EXTINCT BEFORE WE KNOW THAT IT IS THERE - IF IT IS VULNERABLE TO EARTH LIFE**

It's not impossible that Mars life would all become extinct before we know that it is there. Or, we might discover it, but sadly, are unable to find a way to cultivate it in the laboratory before the native life is gone.

That’s especially so because if it is this Woese style pre-LUCA non Darwinian life. Most Earth microbes can’t be cultivated in the laboratory - typically only 1 in 100. Maybe they don’t grow in the standard media used in the labs (e.g. the most extreme acidophiles are hard to cultivate because they depend on finding a suitable media which is as acid as concentrated sulfuric acid), you get the chemical composition of the media wrong, or often - they depend on being part of a community of many other microbes and you have to cultivate the whole thing and can’t just grow one of them on its own.

Or it can be that they are cold loving microbes which have typical lifeimes of months or years - so you need incredible patience to find the right conditions for them to flourish. This is very likely for martian life, that some of it only wakes up properly after it has been in the cultivation media for a month or two - and it then just slowly metabolizes and takes months or years before your first single microbe becomes two microbes.

If only just discovered - how likely is it that we can cultivate some new lifeform based on a totally unfamiliar biochemistry in vitro (in the laboratory, outside its usual biological context).
 * METEORITE TRANSFER ARGUMENTS ARE INCONCLUSIVE**

The arguments about meteorite transfer may seem plausible but they are not at all conclusive especially in the Earth to Mars direction where the meteorites have to leave Earth at Earth escape velocity of 11.2 km/sec after traveling all the way through its thick atmosphere at greater than that velocity with a fireball and plasma evaporating away centimeters in thickness of the surface of the meteorite - and only after the very biggest asteroid impacts like the one that ended the dinosaur era.

It is by no means certain that any Earth life has got to Mars especially given how rare habitats have been on Mars for the last 3 billion years and how hard for an impacting meteorite to get to - and bear in mind any life that survived that sterilizing passage through our atmosphere would be buried deep within a meteorite - and typically gets millinos of years to get to Mars, only a small amount gets there in as short a period as centuries, short enough to not be throroughly sterilized - most would be sterilized to depths of meters so you are talking about a meteorite that has its exterior thoroughly sterilized by heat and plasma ablation, and an interior sterilized to a depth of meters, with right at its heart possibly some surviving microbe that just possibly might be pre-adapted to some habitat on Mars - which the meteorite is unlikely to hit.

Do you see how it is by no means certain that any Earth life has got to Mars? It is posible but if it happened most likely in the early solar system when the Earth was hit by huge impactors hundreds of kilometers across able to blow holes in its atmosphere - and when Mars had oceans. And - was any Earth life back then hardy enough to withstand the journey to Mars?

Nobody knows, if they say they know it is just an educated guess, because different astrobiologists have differing views on what is or is not likely for life on Mars.

For more on this see these sections of my online OK to Touch Mars? book (http://robertinventor.com/booklets/If_humans_touch_Mars.htm)

What about Zubrin's meteorites argument? (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_23_1483228760)
 * Summary (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_24_1483228760)
 * Microbe stowaways on meteorites traveling from Earth to Mars (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_25_1483228760)
 * Case study - can photosynthetic life be transferred from Earth to Mars or vice versa? (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_26_1483332464)
 * More background on whether photosynthetic life could be transferred from Earth to Mars - other photosynthetic species, shock, and spall zone (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#photosynthetic_life_Earth_Mars)
 * General case of transfer of life from Earth to Mars (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_27_1483332464)
 * Microbe stowaways in a human occupied ship (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_26_1483228760)
 * MORE ABOUT THE LAKE**

Short intro:

https://www.youtube.com/watch?v=gksddX9N26wIt was detected using the MARSIS radar on the European “Mars Express” spacecraft orbiting Mars.

The Mars Express spacecraft with its 40-meter MARSIS antenna deployed.

Here is the researcher Robert Oresei explaining in detail how they found it.

https://www.youtube.com/watch?v=zMon3OZ7r8IThis is one of the better more detailed articles about it:
 * Underground Lake of Liquid Water Detected on Mars (https://www.popularmechanics.com/space/moon-mars/a22541370/underground-lake-liquid-water-mars/)

It is covered to a depth of 1.5 km. Although Mars no longer has continental drift, it is still geologically active with features that must have formed in the last few million years. This means it still has internal heat - and there is enough of this to keep a lake like this permanently liquid, because of the insulation of the 1.5 kilometers of ice over the top.

So - this is not thought to be a temporary feature. It is probably permanent. It may be part of an entire system of interconnected sub-glacial lakes on Mars similar to the ones below the ice in Antarctica.

This is a calculation made long ago and scientists have been using radar to try to find these lakes for many years.

As they explained, it is likely to be very cold -10 °C is the maximum temperature because if it was any warmer it would have modified the ice above it to make it less transparent to radar. It may be as cold as - 30 °C and it could be colder, as cold as it is possible for liquid brines to be. This depends on the composition but can be as cold as -60 C. This does not actually rule out biochemistry.

It is too cold for Earth life, the limit is usually cited at -20 °C, around the temperature at which domestic freezers operate (but Earth life’s cold limit is a bit fuzzy because as it gets colder the life slows down more and more and the boundary between dormant and slowly metabolizing is a bit fuzzy).

However on Mars life could have evolved using special antifreezes. For instance one hypothesis is that instead of water and chloride salts, the interior of the cell could use a mix of water with hydrogen peroxide, and with perchlorate cells. Such biochemistry would maybe self destruct at room temperatures, a bit like Earth life at temperatures of 200 °C or higher - but would be able to operate easily at extremely low temperatures.

For more on this see this section of my online OK to Touch Mars? book (http://robertinventor.com/booklets/If_humans_touch_Mars.htm)
 * Life that uses hydrogen peroxide, or perchlorates, or both, INSIDE the cells - habitable to Mars life and not to Earth life (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#hydrogen_peroxide)
 * POSSIBILITY OF HYDROTHERMAL VENTS BELOW THE ICE**

There is evidence that volcanism formed several lakes 210 million years ago on one of the flanks of Arsia Mons (https://news.brown.edu/articles/2014/05/mars). It probably formed two lakes with around 40 cubic kilometers of water each, and a third one of 20 cubic kilometers of water. They probably stayed liquid for hundreds, or even thousands of years, heated from below by a hydrothermal system.

There is evidenc eof eruptions on Olympus Mons as recently as two million years ago (http://www.nature.com/nature/journal/v432/n7020/abs/nature03231.html). There's also evidence of ice near its summit, perhaps even present today, covered by dust.

There could be hydrothermal vents below the ice caps. We wouldn’t know yet if there were. There could also be lakes that formed during large impacts on the polar ice caps and are still there, that would stay liquid for many thousands of years, or if deep enough, permanently.

For more on this see these sections of my online OK to Touch Mars? book (http://robertinventor.com/booklets/If_humans_touch_Mars.htm)
 * Ice covered lakes habitable for thousands of years after large impacts (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#impact_lakes)
 * Ice covered lakes from volcanic activity (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#Temporary_lakes_resulting_from_volcanic_activity)
 * Possibility of geological hot spots in present day Mars (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#Possibility_of_geological_hot_spots_in_present_day_Mars)
 * Life in ice towers hiding volcanic vents (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#fumarole)
 * POTENTIAL SUBSURFACE FRESH WATER MUCH CLOSER TO THE SURFACE - TENS OF CENTIMETERS**

There are lots of ideas for near surface water on Mars - most of them very salty. Even surface life is possible, using the night time humidity, possibly also micropores in salt pillars.

But there is one very intriguing possibility that doesn’t get much attention for some reason.

In Antarctica, fresh water often forms during extremely cold surface conditions just below layers of optically pure transparent ice.

The ice acts like a “solid state” greenhouse - like our atmosphere - trapping heat but letting light through. The light warms up the ice, the heat is trapped by the ice above it, at a depth of a few tens of centimeters - and over a few days in summer the ice melts to create a layer that can be tens of centimeters thick of pure fresh water below the surface ice.

Well - this would happen on Mars too - so long as it also has optically transparent ice like Antarctica. Though the conditions in which the ice forms on Mars is so very different - there may well be optically transparent ice there too - it is very common on Earth.

If so, the low atmospheric pressure won’t matter at all - the water is trapped by the ice above it. The low surface temperatures won’t matter either because ice is a great insulator. In the old days before refrigerators, people would gather ice in winter and store it in buildings below the ground until the summer, and it would stay frozen right through the summer like that.

In the same way - liquid water below the surface of Martian ice would be insulated by the ice above it and would stay liquid from one day to the next. Gradually it would melt more and more until there is a layer of fresh water up to tens of cms thick. This would happen every spring through to summer on Mars.

Their radar can't spot anything like that. But it is one hypothesis for “flow-like” features in Richardson crater near the south pole in the debris from the dry ice geysers that explode out of the surface of Mars in early spring in this crater (the geysers are regarded as an established near certainty - though not actually observed in action, this is the only hypothesis we have for how the dark spots form there every spring).

There are many similar looking “flow like” features on Mars, that seem to have different causese.. Some seem to be due to rolling dry ice boulders hurtling down a slope. Some, in the Northern hemisphere particularly, seem to be due to dust avalanches, or due to salty brines at extremely low temperatures.

But the ones n Richardson' crater have this as one of the two top explanations, fresh liquid water that then pours out from beneath the ice, mixinjg with salt, and then flows down the slope at a rate of sometimes meters per day. The main alternative, under cooled liquid interfacial water, also involves fresh water though in only thin layers that then coalesce and form salty brines.

Möhlmann, inspired by the Antarctica comparison, and the results of his calculations, has suggested that his modeled subsurface water could be a widespread phenomenon in the Mars ice caps (http://www.lpi.usra.edu/meetings/hydrous2009/pdf/4001.pdf), as for Antarctica. Liquid water could form at a depth of around 6.3 cm wherever there is optically clear ice on Mars in snow / ice packs, just as it does in Antarctica. In summer, it could form layers from centimeters to tens of centimeters in thickness.


 * Results of Mohmann's modeling of the solid state greenhouse effect in clear ice on Mars (http://www.lpi.usra.edu/meetings/hydrous2009/pdf/4001.pdf). The plateaus show temperatures that get above the melting point of water regularly every Martian sol, at depths of about 6.3 cms. L here is 11.4 cm. Ice at this level will melt periodically, and especially in summer can stay liquid overnight, leading to layers of subsurface liquid water** cms to tens of cms in thickness. **This should happen on Mars not just in the flow-like Features of Richardson crater, but also, anywhere where there is optically clear ice.

For more on this see these sections of my online OK to Touch Mars? book (http://robertinventor.com/booklets/If_humans_touch_Mars.htm)
 * Southern hemisphere flow-like features - these may involve fresh water! (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_29_1482841503)
 * Creates potential for flowing fresh liquid water on Mars! (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_30_1482841503)

* Interfacial liquid layers model (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#zzee_link_31_1482841503)
 * Could Mars have patches of fresh water in summer, throughout the polar regions, at a depth of six centimeters below optically pure ice? (http://robertinventor.com/booklets/If_humans_touch_Mars.htm#widespread_solid_state_greenhouse)

I don't think there have even been any exeriments to test to see if optically clear ice can form in Martian simulation chambers. But if it can - then this habitat should exist.And if it exists it may be one of the most abundant and most habitable places for life on mars today. And very accessible not 1.5 km down but only tens of cms and with the water and any life in it also probably flowing out onto the surface too
 * PLANETARY PROTECTION DEBATE BY ASTROBIOLOGISTS**

As I said, the topic of planetary protection is a subject of wide ranging debates.

Some advocate searching for life on Mars as quickly as possible on the basis that humans are going to go there sooner or later and that we need to find out what we can before they mess the planet up so much with introduced life that we can’t study any life on Mars in its original state any more:
 * Searching for life on Mars before it is too late (http://online.liebertpub.com/doi/full/10.1089/ast.2017.1703).
 * Is Searching for Martian Life a Priority for the Mars Community? (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5820680/#B49).

Others say that protecting Mars from Earth life should be our top priority and that if we use inadequately sterilized probes in order to get there faster, we risk not finding what we are searching for and messing it up for future astrobiology with the astrobiology missions themselves.
 * Four fallacies and an oversight: searching for martian life (http://online.liebertpub.com/doi/full/10.1089/ast.2017.1749)
 * Inadvertently Finding Earth Contamination on Mars Should Not Be a Priority for Anyone (https://www.liebertpub.com/doi/abs/10.1089/ast.2017.1785?journalCode=ast).

I’d go even futher than that myself. I think we shouldn’t send humans to Mars until we know what life is there. To protect humans too.
 * WE HAVE NO EXPERIENCE OF COLLIDING BIOSPHERES INVOLVING MICROBES THAT USE A FUNDAMENTALLY DIFFERENT BIOCHEMISTRY**

We don’t know what happens when two biospheres collide and there is no guarantee at all that Mars life is safe for Earth, or that Earth life is safe for Mars. Carl Sagan’s example of Legionnaires’ disease is a case in point, as we’ll see, a disease of biofilms that uses the same methods to attack human lungs.

If we use the principle that our biology is adapted to threats it has acutally faced in the past rather than hypothetical threats it has never faced, then, some of the potential results of a biosphere clash could be dire indeed.

We need to know answers to questions like this irst, before we rush in. There is plenty we can do by way of exciting human missions back to the Moon and then studying Mars from an orbital space settlement first, and this is actually a faster way to learn about Mars than with humans on the surface, according to the only study I have found on the topic.
 * ELON MUSK DOES HAVE AN INTEREST IN SCIENCE**

You may wonder how that could be enforced. Well, at present anyway the main palyers do have an interest in science. Elon Musk isn’t anti-science, he is just very pro space colonization.

If he comes to agree with what seems to be the astrobiological consensus that humans on Mars would interfere with potentially importanta astrobiological discoveries - perhaps he may also come to agree that we should focus our attention on the Moon and on telerobotic orbital missions and mission to the Martian moons first, before we make the decision to send humans to the surface.

He also regularly promises early, delivers late. The Falcon Heavy was a flawless launch but long after he first promised it. He was going to send tourists around the Moon in 2018, this is now shelved indefinitely.

He may well continue to promise Mars, but as attention turns to the Moon and that’s where the action is, and where people are paying him to take them, that he sends humans to the Moon first, he is already talking about doing that.
 * IMPOSSIBILITY OF KEEPING EARTH BIOLOGICALLY ISOLATED FROM MARS IF ROCKETS SHUTTLE BETWEEN THE TWO**

In addition though, on my analysis, it seems that there is no way that we can keep Earth biologically isolated from all contact with martian life, if it exists, when humans are returned from Mars having spent time on the surface.

Elon Musk wants to shuttle back and forth with rockets, even if most of the colonists he thinks will go one way to Mars to start with. It seems almost impossible to protect Earth from martian life that could hitch a ride on a BFR that takes off from Mars to land on Earth.

Well, if that is true, Earth is protected not just by the outer speace treaty, but by dozens of laws and international treaties to protect Earth’s environment that have been added to since the 1960s. Even if everyone was agreed that it should go ahead, just the legal processes would take at least a decade. And if done without any knowledge of what there is on Mars and whether or not it poses a risk to Earth, I don’t see how they can get permission to return to Earth.

The Apollo idea of quarantine never had peer review and would not keep out dormant spores in the dust. And microbes from Mars could become part of the human microbiome on the astronauts’ skin. These could easily be harmless to humans, cause no problems and even not be detected on the journey back - and yet be devastating to Earth’s biosphere.

And - we don’t know that Earth life is safe for humans either. As I mentioned,Mars could also in worst case have microbes that infect biofilms, like legionnaires’ disease, seeing our lungs as just a big warm biofilm. It is very unlikely that our antibiotics, designed around specifics of Earth’s microbiology to destroy microbes but keep humans healthy, will work with an alien biochemistry from Mars. They generally target specific molecules and processes and indeed, Earth microbes often become antibotic resistant - well - an alien biochemistry is likely to be so different it is naturally antibiotic resistant.

Then, if you assume that Earth biology has evolved only to protect itself against threats it has actually encountered, rather than hypothetical threats from alien biochemistry that possibly for instance has no proteins, no carbohydrates, no peptides, etc, then there may be no defense against them. this is a point astrobiologists have made ever since Joshua Lederberg, expert on microbial genetics, first started to draw attention to such issues.

A disease of biofilms on Mars using the same mechamisms to attack human lungs, is likely to be more potent if our lungs have never encountered it before. Also if it is alien biochemistry, then antibiotics are likely to have no effect on it, and our body defences may well also not recognize it or mount any resistance if it is based on a radically different form of organic chemistry.
 * HOPE THAT ASTROBIOLOGISTS AND SPACE COLONIZATION HOPEFULS ACAN BE ON THE SAME PAGE**

The astrobiological discussions in the astrobiology journal on both sides assume a situation where astrobiologists are trying to find out as much as possible about Mars biology / biochemistry in the limited time before humans get there. However I think it is possible that space colonization advocates can come to see a value in finding out about the astrobiology of Mars before committing to landing there, and to learn about potential hazards for both their astronauts and Earth in advance.

If Elon Musk or other Mars hopefuls agree with this assessment then they also should be as keen as anyone to know what kind of life there is on Mars.

And - if they don’t, but at least some of the expert astrobiologists consulted by the politicians say that this is possible, you can be sure that attempts to get permission to return to Earth after visiting Mars will run into many legal issues.

I think that if a human mission to Mars or a mission that sends large rockets to Mars and back with no possibility of “breaking the chain of containment” actually becomes a real possibility, which it isn’t yet, all this will get a public airing and will have to go through the courts.

Elon Musk can’t direct law makers in the US to permit him to do illegal things (in this case, return materials from Mars without establishing that it is safe for Earth’s environment to do this first). It doesn’t matter how many sympathizers he gets, or how popular and well liked he is, he still has to go through due process like everyone else.

It would have to be a case of changing the law to make it legal. That takes a long time, if it can be done at all. Or - to prove that there is no risk to Earth even fron unknown astrobiology on Mars, wthin the existing laws - all of that seems immensely challenging.

For this reason I am not concerned about what might happen to Earth, but rather, about disappointments after unrealistic expectations by Mars colonization hopefuls.

I hope we can all be on the same page on this matter.
 * RAPID ASTROBIOLOGICAL SURVEY OF MARS TELEROBOTICALLY FROM ORBIT**

If instead of fighting each other, we work together for a vigorous early astrobiological survey of Mars using robots from Earth, 100% sterile (in my view) and then once we have the capability to send humans to Mars orbit safely - then operated telerobotically from orbit around Mars and from its two moons.

With reduced cost for heavy lift in the near future - and with the enthusiasm and extra funding that might accompany a spectacular human mission to Mars orbit and its two moons, we might be able to do this as quickly as in 10 years from the first human mission to Mars orbit - and it is an interesting and challenging mission for our astronauts too.

Probably it will take an additional ten years or so of missions closer to hand, for instance on the Moon, before we have enough confidence in life support to send humans to Mars (unless transit times to Mars are reduced hugely), because it is so far away, with no prospectof a quick abort back to Earth. It would be possible to rush this but with a great risk of astronauts dying in an “Apollo 13” type accident during the years long journey to / from Mars orbit with no possibility of the happy ending for that mission.

Once we know the answers, we can then make decisions based on knowledge of what is there. This will be far easier than the current situation where we have to try to reason about what might happen as a result of accidentally returning any microbe of any concievable biochemistry from Mars. By way of example, if we only find pre-biotic chemistry on Mars, there is no risk of environmental damage of Earth - but risk of losing research of great science value on Mars. If we find aggressive microbes that can kill humans by eating their lungs on Mars then everyone would probably agree we need to proceed with extreme caution. There are many other possible outcomes and attempting a guess on what we find and what options we have is likely to be unreliable just like the attempts in the 1970s and earlier to guess on the technology and science of the 21st century.

For more on all this, see my:
 * Why explore Mars from orbit? (http://www.science20.com/robert_walker/will_first_mars_astronauts_have_to_stay_in_orbit_teleoperating_sterile_surface_rovers_to_prevent_collidng#zzee_link_1_1527369586)
 * What would astronauts think about a mission where they orbit Mars or land on its moons but never land on its surface? answers by Eileen Collins and Tom Jones (http://www.science20.com/robert_walker/will_first_mars_astronauts_have_to_stay_in_orbit_teleoperating_sterile_surface_rovers_to_prevent_collidng#astronauts_views)
 * How astronauts returning from Mars will mean we need to protect Earth (http://www.science20.com/robert_walker/will_first_mars_astronauts_have_to_stay_in_orbit_teleoperating_sterile_surface_rovers_to_prevent_collidng#zzee_link_2_1527369586)
 * Won’t the Martian surface be sterile? (http://www.science20.com/robert_walker/will_first_mars_astronauts_have_to_stay_in_orbit_teleoperating_sterile_surface_rovers_to_prevent_collidng#zzee_link_3_1527369586)
 * What are the chances of life on the Mars surface? Views of experts (http://www.science20.com/robert_walker/will_first_mars_astronauts_have_to_stay_in_orbit_teleoperating_sterile_surface_rovers_to_prevent_collidng#chances_of_life)
 * My background - keen on humans in space - but also value science and the environment of Earth (http://www.science20.com/robert_walker/will_first_mars_astronauts_have_to_stay_in_orbit_teleoperating_sterile_surface_rovers_to_prevent_collidng#zzee_link_4_1527369586)
 * Outer Space Treaty is not as strong as you might think for the private sector (http://www.science20.com/robert_walker/will_first_mars_astronauts_have_to_stay_in_orbit_teleoperating_sterile_surface_rovers_to_prevent_collidng#zzee_link_5_1527369586)
 * Legislation to protect Earth’s environment has real teeth to it (http://www.science20.com/robert_walker/will_first_mars_astronauts_have_to_stay_in_orbit_teleoperating_sterile_surface_rovers_to_prevent_collidng#zzee_link_7_1527369586)
 * What happens for an astronaut? (http://www.science20.com/robert_walker/will_first_mars_astronauts_have_to_stay_in_orbit_teleoperating_sterile_surface_rovers_to_prevent_collidng#zzee_link_10_1527369586)

and other sections in my
 * Will First Mars Astronauts Stay In Orbit - Tele-operating Sterile Rovers - To Protect Earth And Mars From Colliding Biospheres? (https://www.science20.com/robert_walker/will_first_mars_astronauts_stay_in_orbit_teleoperating_sterile_rovers_to_protect_earth_and_mars_from_colliding)
 * SEE ALSO**
 * Likely 2040 Before Mars Samples Returned Safely, Legally -Yet Not Likely To Return Life - Needs To Be Detected In Situ First (http://www.science20.com/robert_walker/likely_2040_before_mars_samples_returned_safely_legally_yet_not_likely_to_answer_astrobiology_questions-232052)
 * Protecting Mars - And Earth - From What - And Why Bother? Our Inheritance Of Unopened Astrobiological Treasure Chests (https://www.science20.com/robert_walker/protecting_mars_and_earth_from_what_and_why_bother_our_inheritance_of_unopened_astrobiological_treasure_chests)

My online book (free to read online and also available for purchase for a modest fee on Kindle):

Touch Mars? Europa? Enceladus? Or a Tale of Missteps? (http://robertinventor.com/booklets/If_humans_touch_Mars.htm)

You may also be interested in some of my other recent blog posts at Science 2.0 on related topics (https://www.quora.com/What-would-it-take-to-access-the-newfound-lake-on-Mars-without-risking-its-destruction-e-g-by-depressurization/answer/Robert-Walker-5/comment/68955375).