Right now all our missions to Mars are sterilized to protect it from any Earth life that could hitch a ride and confuse the searches. A report by the “Planetary Protection Independent Review Board” recommends that NASA treats most of Mars similarly to the Moon for planetary protection. It comes with a cover letter from NASA recommending to their planetary protection officer that they implement the proposal. This would be fine if Mars was like the Moon. However, new discoveries show that Mars has liquid water there, in the form of brines, just a few centimeters below the surface. The measurements are indirect because we can't visit most of these locations yet and can't drill down even a few centimeters. There is now clear evidence of very cold brines even beneath the surface of the sand dunes that Curiosity drives over.

Their suggestion is to reclassify large parts of Mars as Category II (current classification for the Moon), meaning that there are no niches where terrestrial microorganisms could proliferate, or a very low likelihood of transfer to such places.

… where there is only a remote chance that contamination carried by a spacecraft could jeopardize future exploration”. In this case we define “remote chance” as “the absence of niches (places where terrestrial microorganisms could proliferate) and/or a very low likelihood of transfer to those places.

COSPAR Workshop on Planetary Protection for Outer Planet Satellites and Small Solar System Bodies European Space Policy Institute (ESPI), 15–17 April 2009

As far as I know mine is the only article to suggest that there may be very significant downsides to dropping planetary protection - most of what you see are articles praising NASA for moving with the times, and making things easier for commercial space and future planetary colonization.

(skip to What about the forwards direction? )

Curiosity can't drill down to examine the brines it detected indirectly, and also is not equipped with any specific life detection instruments. It can detect some organics related to life, but only after heating them up in a small oven until they decompose, then it analyses the evolving gases. Those particular brines are probably too cold for Earth life, but biofilms could create microhabitats to make them more habitable and there are suggestions for several other microhabitats in the equatorial regions that may be more habitable than the Curiosity brines.

The Moon has nothing like that.

The new report has few cites, and its main cite for this proposal is a controversial 2014 report. While the 2014 report was in process of publication, NASA and ESA took steps to get it independently reviewed. This 2015 independent review said the maps from the 2014 report are most useful if they accompanied by cautionary remarks that they represent incomplete knowledge. This new report by the “Planetary Protection Independent Review Board” doesn't cite the 2015 review or mention these criticisms of the main cite they rely on.

Overlay in white text: : "2015 review says maps represent incomplete knowledge. Extraterrestrial microbes may be here in salty brines just below the surface. Introduced Earth microbes could extinguish second genesis on Mars". Map from the 2014 report. Text summarizes one of the main criticisms of this report in the 2015 review.

It’s important to get this right as there is no way to do a “do over”. It would be so sad to get to Mars, find life there, and then realize it was just life we brought ourselves. For many, the search for other lifeforms in our solar system is one of the major motivating reasons to explore Mars and other parts of our solar system with a potential for life.

This would also impact on the science interests of other countries. That includes the future discoveries of ESA (Europe), ROSCOSMOS (Russia), JAXA (Japan), ISRO (India), CNSA (China) and any other nation with an interest in exploring Mars. It's far easier to detect martian life, and know that it is from Mars, if there is no introduced Earth life there.

What we find on Mars could be absolutely unique. We can't make even the simplest of living cells from non living chemicals. We can make, or modify DNA, and we can insert DNA into a cell and use it to modify how it functions. However this only works if we have a pre-existing cell to modify. We can't make a new living cell from scratch. We don't know the details of all the chemical and physical processes that make up the simplest living cell, but even if we did, we still can't make it. Any attempt to build even the simplest RNA world cell, even if we knew the exact position of every atom in it, would fail. As soon as we start to assemble the chemical constituents they would react together to make a chemical mush. Our attempts to assemble early life in the laboratory (e.g. in the Szostack lab) are based on trying to accelerate chemical evolution, not assembling it from scratch. As Cairns-Smith put it in his "Seven Clues to the Origin of Life" (which approaches the problem of the origin of life like a detective puzzle modeled after Sherlock Holmes novels):

"Subsystems are highly INTERLOCKED within the universal system. For example, proteins are needed to make catalysts, yet catalysts are needed to make proteins. Nucleic acids are needed to make proteins, yet proteins are needed to make nucleic acids. Proteins and lipids are needed to make membranes, yet membranes are needed to provide protection for all the chemical processes going on in a cell. It goes on and on. The manufacturing procedures for key small molecules are highly interdependent: again and again this has to be made before that can be made - but that had to be there already. The whole is presupposed by all the parts. The interlocking is tight and critical. At the centre everything depends on everything"

(page 39 of Seven Clues to the Origin of Life)

If native martian life is especially vulnerable, for instance some form of early life, pre-DNA, we might make it extinct. There would then be no way to reconstruct it, even if we later found clues to how it worked before we made it extinct. This could also impact on the future commercial potential for Mars. Enzymes derived from extremophiles are already the basis for a billion dollar global industry. If we can find life based on a different biochemistry, this has a vast commercial potential. For details see Billions of dollars commercial potential of extraterrestrial biology (below).

Microhabitats for life and shallow subsurface habitats on Mars are likely to be undetectable from orbit. The harsh ultraviolet light would cause even surface lichens to huddle into partial shade in cracks and crevices. as they do in the high Antarctic mountains. Similarly it would be impossible to see life hidden beneath the surface of rocks, or beneath a mm or so of dust or deeper down in the top few centimeters of the Martian surface where, as we'll see, there are possibilities that conditions may be habitable for native as well as introduced Earth life.

The 2015 review found that maps of surface features" can only represent the current (and incomplete) state of knowledge for a specific time".

Text on image: Lichens on Mars would huddle in partial shade protected from UV, like this lichen in high mountains in Antarctica. It could not be seen from orbit with 30 cm resolution.

Pleopsidium chlorophanum in Antarctica From DLR press release Surviving the conditions on Mars

Pleopsidium chlorophanum on granite, collected at an altitude of 1492 m above sea level at "Black Ridge" in North Victoria Land, Antarctica. This photograph shows its semi-endolithic growth in Antarctic conditions. You can see that it has fragmented the granite, and that pieces of the granite are partly covering it, possibly helping to protect from UV light. Photograph credit DLR

See Lichens, cyanobacteria and molds growing in humidity of simulated Martian atmosphere

There are some dark hillside streaks near to the Curiosity landing site that grew and shifted in ways that suggested the presence of flowing water below the surface. Because of the possibility that these streaks could be habitable, Curiosity has to avoid them, because it is not sterilized sufficiently to go up to them to examine them. Importantly, these streaks were not discovered until after Curiosity landed on Mars. Also they are not proven to be dust cascades, as some say. It's one hypothesis that may have some truth to it, but there are many issues with it, such as the seasonality correlated with warmth and not correlated with winds, that the streaks fade too quickly over weeks rather than decades, and are too narrow for dust, and the problem of resupply from the top every year. Though the stopping angle matches the motion of cohesionless dust, there is likely to be liquid brines involved as well. See Dust cascades explanation,

If there is life on Mars, it's likely to be sparse and slow growing, like the life in our coldest driest deserts. Depending how much life is there, it may have almost no effect on the atmosphere, but it might have some effects we can notice. Curiosity has recently discovered variations in oxygen. Some process on Mars is creating more oxygen than expected in spring to summer, and less in mid winter, and the only correleation they have found is that less oxygen is produced when there is more dust in the atmosphere. They didn't find a correlation with seasonal and interannual pressure vartiation, or temperature variation. Could it be photosynthetic life? We also have the intriguing methane plumes also confirmed by ESA's trace gas orbiter.

Cassie Conley who used to be planetary protection officer for NASA puts it like this, as reported by Scientific American

“We’ve got engineers who are convinced that they know everything and biologists who still acknowledge that we still don’t know very much. Fundamentally, that is the dispute.”

Here is a video I made for this article (while working on the draft)

(click to watch on Youtube)

This article will focus on the forwards direction, the risk of sending Earth microbes to Mars because the legal protection in that direction is very weak.

In the backwards direction the legal protection is very strong indeed, far more than it was at the time of Apollo. Margaret Race of the SETI institute mapped out the laws that NASA would have to navigate to return a sample to Earth. I figure out, based on her list, that they should have started work on the legal process in 2010 or earlier to return a sample by 2032 as they plan. So, I don't think they are going to return it to Earth unsterilized myself. Most likely sterilize it, or return it to somewhere not in contact with Earth such as telerobotic study above GEO.

At any rate there is no risk of harm to Earth's biosphere. It would be looked at in great detail over a period of years and expert astrobiologists would be called as witnesses to testify and help keep Earth safe. For details about that, skip to Earth has strong legal protection/


Skip to: 2015 review and problems with maps

Since Earth is well protected in the backwards direction, for a sample returned from Mars, the main concern is for the forwards direction. Unlike the backwards case, there isn’t any other legislation here to protect Martian life apart from the weak Outer Space Treaty. All the rules for planetary protection are based on a few phrases about “harmful contamination”. They have been interpreted as including "harmful to the scientific experiments of other parties to the treaty".

I think the way ahead here is to make sure everyone is on board and understands the importance of planetary protection - for scientists - and for colonization enthusiasts too. It's important for all of us to know what is there, and if there is life there that could harm humans or Earth's biosphere, or whether astronauts could impact adversely on martian life.

If these proposals were adopted in the forwards direction, you could send what you like to these regions of Mars, tardigrades, and extremophile blue green algae that have already been tested in Mars simulation chambers. The only requirement would be to document what you do. Eventually you could send humans too, with this category II classification, though returning them would be another matter if they had made contact with extraterrestrial microbes on Mars.

The report is here together with a cover letter from NASA recommending to their planetary protection officer that they implement the proposal:

One of their main cites is a report from 2014 by Rummel et al which proposed the use of maps to divide Mars into special regions which need especially careful planetary protection measures such as was used for the Voyager landers in the 1970s, and others that have less stringent requirements such as is used for Curiosity:

This is the basis for their proposal that Mars could be subdivided into regions some reclassified as category II. Although they don’t go into detail, presumably they would use a map like the one in the 2014 review, and classify all except the uncertain regions as category II:

Map from the 2014 report. Purple is low in elevation, and grey is higher elevation. Red and blue lines delineating regions are approximately 50 km in width

In the text overlay I summarize the objection to this map in the 2015 review "2014 map of uncertain regions of habitability. 2015 review says maps can only represent incomplete knowledge."


Skip to: Vigorous debate in Nature and Astrobiology journal

Even before Rummel et al’s report was published, both NASA and ESA took steps to have it reviewed independently.

This 2015 review overturned several of the findings of the 2014 report, and in particular, it recommended against the use of maps [49] saying:

In general, the review committee contends that the use of maps to delineate regions with a lower or higher probability to host Special Regions is most useful if the maps are accompanied by cautionary remarks on their limitations. Maps … [of] surface features can only represent the current (and incomplete) state of knowledge for a specific time—knowledge that will certainly be subject to change or be updated as new information is obtained.

5 Generalization of Special Regions and the Utility of Maps

This new NASA report doesn’t mention the 2015 review. It’s an extraordinary omission from a report that is recommending the use of maps for category II.

I don’t know the reason for this omission. They certainly should have looked at this 2015 review, and not just at the original 2014 report, before making this recommendation to NASA to map out large parts of Mars as category II like the Moon.

The 2015 report used the example of Recurring Slope Lineae (RSLs) to explain why maps are not enough by themselves. These are seasonal streaks that form on sun facing Martian slopes. They appear in the Martian spring, grow and broaden through the summer and fade away in autumn.

These dark features are not themselves damp and may be dust flows. However, they are associated with hydrated salts and they may also be linked with salty water (brines) in some form. Sadly the HiRISE instrument can only observe them in the early afternoon locally, the driest time for the Martian surface, because of its high inclination sun synchronous orbit. This makes it especially hard to know if there are any brines moving down these slopes.

Warm Season Flows on Slope in Newton Crater (animated)

The first ones were found in higher latitudes, but many of these have now been found in the Martian “tropics”, especially on the slopes of the Valles Marineres. Their status is unknown, whether they could have habitats for Earth life or not. At present they are classified as

“As such they meet the criteria for Uncertain Regions, to be treated as Special Regions.” [a “Special region” is one that Earth microbes could potentially inhabit]

The 2015 review gives the example of the ExoMars Schiaparelli lander. All HiRISE images of the landing site were inspected for the possible presence of RSL's. [50]

As another example of this, 58 RSLs were found on Mount Sharp close to the Curiosity landing site.

Here are some of them:

Possible RSLs on mount Sharp not far from the Curiosity rover. These photos are taken at a similar time in the Martian year, they are less prominent in the earlier one in 09 March 2010 and more prominent with some new ones in the later image August 6 2012. Photo from supplementary information for Transient liquid water and water activity at Gale crater on Mars

Importantly, these were not discovered until after the Curiosity landing in 2012. See Slope activity in Gale crater, Mars (2015) and Nature article: Mars contamination fear could divert Curiosity rover

This shows that we mightn’t always be able to rule out potential uncertain regions that could be habitats at a landing site. They may be discovered later, after the landing itself.

More RSLs have been found in the Mawrth Vallis region, one of the two final candidates for ExoMars landing site

These results denote the plausible presence of transient liquid brines close to the previously proposed landing ellipse of the ExoMars rover, rendering this site particularly relevant to the search of life. Further investigations of Mawrth Vallis carried out at higher spatial and temporal resolutions are needed to …, to prevent probable biological contamination during rover operations, …

Discovery of recurring slope lineae candidates in Mawrth Vallis, Mars

ExoMars isn’t going to Mawrth Vallis, because they chose the other candidate Oxia Planum. I can’t find anything about RSLs in Oxia Planum, but how confident can we be that this doesn’t have RSLs or other potential habitats? Does non detection so far mean they aren’t there?


Skip to: Important habitats not covered by 2014 report

This new report also doesn’t mention the long running and vigorous debate on the topic of whether we should relax sterilization requirements for spacecraft sent to Mars.

This debate started in two Nature articles in 2013 and has continued in Astrobiology journal through to 2019.

Both sides in this debate were in agreement that there is a significant possibility that Earth microbes can contaminate Mars.

Surely neither side in this debate would support classifying most of Mars as category II like the Moon.

Rather, the argument in Nature and Astrobiology journal is about whether we should reduce sterilization requirements for Mars in order to study these potential habitats quickly before human missions get there and make it impossible to study them in their pristine condition without Earth life.

The other side in this debate argue that we have a fair bit of time before humans get there, and that if we relax planetary protection we risk finding Earth microbes we brought there ourselves.

Those arguing for relaxing planetary protection are:


This debate is not mentioned in this report.

Nor does it mention the many new potential surface or near surface habitats that have been proposed / indirectly detected / theorized since 2008. We have had more of these than there have been years since 2008.


Skip to: Nilton Renno's droplets

  • microscale habitats that can't be detected from orbit.

The 2014 report briefly considers these. The 2015 review expands on this topic, and says that to identify such potential habitats requires a better understanding of the temperature and water activity of potential microenvironments on Mars, for instance in the interior of craters, or microenvironments underneath rocks. These may provide favourable conditions for establishing life on Mars even when the landscape-scale temperature and humidity conditions would not permit it. [46]

  • Ice close to the surface needs to be taken account of for spacecraft induced special regions.

The 2014 report looked at distributions of ice and concluded that ice in the tropics is buried too deep to be a consideration[47]

However the 2014/5 review corrected this due to evidence of ice present at depths of less than one meter in pole-facing slopes[48]

Research since then still hasn’t resolved these issues.

Even the 2014 report acknowledged limitations:

"Claims that reducing planetary protection requirements wouldn't be harmful, because Earth life can't grow on Mars, may be reassuring as opinion, but the facts are that we keep dis4g life growing in extreme conditions on Earth that resemble conditions on Mars. We also keep discovering conditions on Mars that are more similar—though perhaps only at microbial scales—to inhabited environments on Earth, which is where the concept of Special Regions initially came from."

"A New Analysis of Mars "Special Regions": Findings of the Second MEPAG Special Regions Science Analysis Group (SR-SAG2)" (PDF).

Skip to: Does this matter:


I’d like to cover a couple of these potential habitats to motivate this, then I’ll look at why it is so important to protect Mars from Earth life - is it really so important to make sure we don’t mix Earth life with Mars life before we canstudy it?


Skip to: Curiosity brines

Nilton Renno's droplets that form where salt touches ice - why did he call a droplet of salty water on Mars "a swimming pool for a bacteria"?

This is perhaps one of the most striking discoveries in recent years because of its implications for habitability of Mars. Nilton Renno found that liquid water can form very quickly on salt / ice interfaces. Within a few tens of minutes in Mars simulation


Erik Fischer, doctoral student at University of Michigan, sets up a Mars Atmospheric Chamber on June 18, 2014. These experiments showed that tiny "swimming pools for bacteria" can form readily on Mars wherever there is ice and salt in contact.

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

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

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

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

(transcript from
1:48 onwards)

(click to watch on Youtube)

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


Skip to: Effects of biofilms

This was a serendipitous discovery announced in April 2015. Liquid brines that form through deliquescing salts (perchlorates) - the salts take in water from the atmosphere (same principle as the salts you use to keep equipment dry).

They noticed that when Curiosity drives over sand dunes, then the air above them is drier than it is normally. When it leaves the sandy areas the humidity increases.

Rover Environmental Monitoring Station (REMS) on NASA's Curiosity Mars rover

It’s temperature and humidity sensors are located on these booms on the rover’s mast

NASA Mars Rover's Weather Data Bolster Case for Brine

This shows that something in the sand dunes is taking up water vapour from the air, and rather a lot of it too. They calculated that the perchlorates in the sand must take up so much water at night that the liquid brines would be habitable, except that they are too cold for Earth life. This shows how it works:

As the day progresses the brines warm up but any brines close to the surface (in the top five centimeters or so) would dry out, and become too salty for Earth life. That's for any water in the top five centimeters or so.

They found conditions for liquid water in the top 5 cms at various times in the morning for most of the year from 2 am to after 8 am, and in the evening in winter from 6 pm to around midnight (just reading off from their figure 3b)

However, when temperatures in the top 5 cms reach conditions habitable for Earth life, they find that the water activity has dropped to zero, making it impossible for Earth microbes to replicate (Earth life requires a water activity level of at least 0.6). More strictly speaking, microbes may be able to replicate at lower temperatures but if so, it’s exceedingly slow, centuries to thousands of years.

Planetary protection at present at least is based on keeping Mars free of Earth life only for our own purposes and not for future generations thousands of years from now, so they count habitats as being okay for planetary protection if the conditions are so cold that life would take millennia to colonize it.

They suggest that it could have permanently hydrated brines below about 15 centimeters below the surface, and at that depth, the liquid would never get warm enough for metabolic activity for Earth microbes, never mind replication.

Top temperatures in summer at 15 cms depth would be around -40 °C (I'm reading this off their figure 2a, grey shows the temperature range 15 cm below the surface).

The authors of the paper concluded that the conditions in the Curiosity region were probably beyond the habitability range for replication and metabolism of known terrestrial micro-organisms. However this is in the tropics where the air is (comparatively) warm and dry, and it leads to the possibility of habitable brines in conditions that are colder, with greater atmospheric water content.

As perchlorates are widely distributed on the surfaceof Mars, this discovery implies that the rest of the planet should possess even more abundant brines owing to the expected greater atmospheric water content and lower temperatures

For a summary see "Evidence of liquid water found on Mars (BBC)" and for the article in Nature "Transient liquid water and water activity at Gale crater on Mars" (abstract, the paper is behind a paywall, but you can read it via the link in the BBC article through Springer Nature Sharedit,. or researchgate).

"Gale Crater is one of the least likely places on Mars to have conditions for brines to form, compared to sites at higher latitudes or with more shading. So if brines can exist there, that strengthens the case they could form and persist even longer at many other locations, perhaps enough to explain RSL activity,"

Principal Investigator Alfred McEwen

NASA Mars Rover's Weather Data Bolster Case for Brine


Skip to: What are these recurring slope lineae?

Does this really mean that the brines are sterile though - for either Mars or Earth life?

Nilton Renno, who is an expert on Mars surface conditions suggests that Earth microbes may still be able to exploit this liquid brine layer through biofilms::

"Life as we know it needs liquid water to survive. While the new study interprets Curiosity's results to show that microorganisms from Earth would not be able to survive and replicate in the subsurface of Mars, Rennó sees the findings as inconclusive. He points to biofilms—colonies of tiny organisms that can make their own microenvironment."

Mars liquid water: Curiosity confirms favorable conditions.

The 2015 review makes a similar point about the ability of multi-species microbial communities to alter dispersed small-scale habitats.

Cells in biofilms are embedded in a matrix of externally produced substances (such as polysaccharides, proteins, lipids and DNA) and adjust environmental parameters to make them more habitable[45]. There are many examples of small-scale and even microscale communities on Earth including biofilms only a few cells thick. Microbes can propagate in these biofilms despite adverse and extreme surrounding conditions.

NOTE ON FOOTNOTES: the footnotes here link to my Astrobiology Encyclopedia. This has corrected and extended versions of Wikipedia articles on the same topic, which have many mistakes and omissions (for instance, Wikipedia doesn’t mention the 2015 review).

I don’t know if Nilton Renno meant a martian biofilm or one for Earth life. However both could work.

Martian life would surely be adjusted to live at the lowest temperatures on Mars. It could do that using the chaotropic agents such as the perchlorates which are naturally present on Mars - these are chemicals that help processes to continue at lower temperatures than they usually do. Earth life may be able to use these too. 2014 report mentions these:

3.1.3. Chaotropic substances. Numerous types of com-pounds increase the flexibility of molecules, destabilizing and/or fluidizing them

Mars has abundant chaotropic agents

Chaotropes such as MgCl2, CaCl2, FeCl3, FeCl2, FeCl, LiCl, perchlorate, and perchlorate salts are, collectively, abundant in the regolith of Mars.

These would permit faster metabolic processes at lower temperatures.

The 2014 report has a finding

Finding 3-3: Chaotropic compounds can lower the temperature limit for cell division below that observed in their absence. There exists the possibility that chaotropic substances could decrease the lower temperature limit for cell division of some microbes to below-18°C (255 K), but such a result has not been published.

I haven’t found much research on the topic since then. Here are a couple of relevant papers but these are preliminary results:

If you know of more on this topic do say.

If it is possible for life to evolve to live in these habitats, then conditions on Mars would seem to be optimal to drive such evolution

  • Chaotropic agents abundant in the Martian salts
  • Salty brines rich in these chaotropic agents with extreme low temperatures also likely abundant, in the top 15 cms throughout the equatorial regions.

Surely there is a possibility here that martian biofilms have evolved to take advantage of these brines.

If they have done so they would likely trap the water at night at those low temperatures below - 40 C and then retain it in the films through to daytime as the brines warm up to temperatures conducive to Earth life.

So, the Curiosity brines could well be habitable to martian life. They may be habitable to Earth life too - though at those low temperatures it would likely reproduce only slowly. But if the biofilm retains liquid water through to daytime there isn’t really any limit on how warm it could get and still retain liquid within the biofilm that perhaps Earth life could colonize.

There are many other potential microhabitats on Mars, even in equatorial regions. For a couple of examples see Microhabitats - such as micropores in salt pillars and ground hugging water vapour as morning frosts evaporate  in my preprint.

Also there may be underground caves that communicate with the surface. These would be of many different types on Mars, as varied as on Earth and some formed by processes unique to Mars involving dry ice, or rare on Earth involving sulfuric acid. Most of them won’t be easy to spot from orbit, just as caves on Earth are hard to spot from orbit, with entrances that are often hard to see even when you approach them on the ground. Penelope Boston lists some of the types of cave possible on Mars (Boston, 2010)

  1. Solutional caves (e.g. on Earth, caves in limestone and other materials that can be dissolved, either through acid, or water). The abundance of sulfur on Mars may make sulfuric acid caves more common than they are on Mars.

  2. Melt caves (e.g. lava tubes and glacier caves)

  3. Fracture caves (e.g. due to faulting)

  4. Erosional caves (e.g. wind scoured caves, and coastal caves eroded by the seas on ancient Mars)

  5. Suffosional caves - a rare type of cave on the Earth, where fine particles are moved by water, leaving the larger particles behind - so the rock does not dissolve, just the fine particles are removed.

  6. Sublimational caves caused by dry ice and ordinary ice subliming directly into the atmosphere (a process that doesn’t occur on Earth).

See also these sections of my preprint:

Some think that it is possible that Mars has fresh liquid water in polar regions, a few tens of centimeters below the surface, protected from the surface vacuum by clear ice and melted by the solid state greenhouse effect. This should happen according to the models if Mars has ice similar in properties to the clear blue ice in Antarctica (where a similar process occurs).

Perhaps there could even be liquid water in equatorial regions too when the early morning frost (discovered by Viking) melts. This is preliminary unpublished research at present.

Andrew Schuerger’s lab at the University of Florida recently made a startling, albeit preliminary, discovery. He tested the effect of frost (first discovered on Mars by the Viking mission) on rocks under Martian conditions, and found that liquid water flowed on the rocks for about 15 minutes, before all the water turned into the gas phase.

Life could exist on Mars today, very close to the surface - AirSpace magazine

There have been at least as many new proposed near surface habitats for Mars since the striking Phoenix leg droplet observations in 2008 as there have been years.

Then let’s look briefly at the RSLs, top candidate for many astrobiologists.


Skip to: Dust cascades explanation

Many dark streaks form seasonally on Mars. Most of these are thought to be due to dry ice and wind effects. This image shows an example, probably the result of avalanche slides and not thought to have anything to do with water:

Slope Streaks in Acheron Fossae on Mars - these streaks are thought to be possibly due to avalanches of dark sand flowing down the slope

Notice that these avalanche streaks are dark, and broad. They take decades to fade away.

However a few of the streaks form in conditions that rule out all the usual mechanisms. These are the Warm Seasonal Flows, also known as Recurrent Slope Lineae.[100]

  • They form on sun facing slopes in the summer when the local temperatures rise above 0C so far too warm for dry ice.
  • They are not correlated at all with the winds and dust storms.
  • They are also remarkably narrow and consistent in width through the length of the streak, when compared to a typical avalanche scar.
  • They develop seasonally over many weeks, gradually extending down the slopes through summer - and then fade away in autumn

  • Warm Season Flows on Slope in Horowitz Crater (animated)

The leading hypotheses for these remains that they are correlated in some way with the seasonal presence of liquid water - probably salty brines.


Skip to: Why life on Mars need not be related to Earth life

A 2017 paper did show that the some aspects of these features are more consistent with dust cascades. That got widely reported (if you follow the news on Mars astrobiology), but what hasn’t been reported so much are the many difficulties with this explanation, which suggest it is only part of the picture. I found those through literature searches rather than news stories.

These papers suggest they are not yet fully understood and may still contain substantial amounts of brines. I wrote a summary of this research for a draft astrobiology article I’m working on myself (work in progress) (cites here take you to my version of the article in google docs)

The Recurring Slope Lineae (RSL’s) remain a leading candidate for brines that could be habitable, although there is considerable debate in the literature about the amount of brines present and whether they may be habitable. In planetary protection discussions since they may be the result of aqueous processes they are treated as “an Uncertain Region that is to be treated as a Special Region until proven” (Rettberg et al, 2016).

A study of RSLs in Eos Chasma shows that the features are consistent with dust cascades, since they terminate at slopes matching the stopping angle for granular flows of cohesionless dust, and they also ruled out formation of substantial quantities of crust‐forming evaporitic salt deposits, though the hydrated salts and seasonal nature continue to suggest some role for water in their formation (Dundas et al, 2017).

Difficulties with the dust explanation include the rapid fading away of the streaks at the end of the season, instead of the more usual decades, and a lack of an explanation of how the dust is resupplied year after year. Resupply also remains a major question for the models involving substantial amounts of liquid brines (Stillman quoted in David, 2017). A study of RSLs in the Valles Marineres finds that they seem to traverse bedrock rather than the regolith of other RSLs, and that if water is involved in their formation, then substantial amounts must be needed to sustain lengthening throughout the season (Stillman et al, 2017).

I will be citing from my preprint here, registered with the Open Science Foundation, but will just be using it here for its literature summaries:

Potential Severe Effects of a Biosphere Collision and Planetary Protection Implications


Skip to: What is the problem with bringing Earth life to Mars?

The Chicxulub impactor did send material from a shallow tropical ocean to Mars, 66 million years ago, but it would be hard for a microbe to withstand the shock of impact, fireball of ejection from our atmosphere, ionizing radiation, cold and vacuum of space, and then to find a home on present day dry and dusty Mars congenial to it.

If there is Earth life there, it’s most likely transferred billions of years ago when Mars had seas and big asteroids tens to hundreds of kilometers in diameter hit Earth able to punch a hole in our atmosphere and send rocks all the way to Mars with relatively little by way of shock or atmospheric heating.

In the other direction, if it is native Mars life we don’t know its capabilities but it could easily be damaged beyond recovery by the instant shock of ejection from the Mars surface - and all of the meteorites we have at present come from at least a couple of meters below the surface and ejected from the southern uplands where the air is thinner so that smaller impacts can send material all the way to Earth. The most likely habitats for martian life are also fragile - dust, ice, salts, and it would not be easy for life in those to get to Earth.

Again the easiest time for martian life to get to Earth is in the early solar system when Mars had seas, and later, lakes, and then it depends on its capabilities back then, whether it could do this.


Skip to: Prestige or dishonour - first footsteps on Mars

It’s easy to find life if we bring it there ourselves.

Cassie Conley, former planetary protection officer for Mars puts it like this:

(click to watch on Youtube)

33 seconds into this video “So we have to do all of our search for life activities, we have to look for the Mars organisms, without the background, without the noise of having released Earth organisms into the Mars environment.”

Full quote:

The idea of bringing microbes to Mars, in order to sort of test whether Mars could be a habitat, whether we could terraform Mars, whether it could be a habitat for Earth organisms -- that's something we might do eventually. If the international community decides it's the right thing to do, we can certainly do it. It's just that as we go about the process of exploring Mars, we don't want to screw up the things we want to do first by doing things that then we can't take back afterwards.

We can't do a do-over on releasing organisms in the Mars environment. Once they're there they will be there. So we have to do all of our search for life activities, we have to look for the Mars organisms without the background, without the noise of having released Earth organisms into the Mars environment. This is why we are very careful when we clean robotic spacecraft, because we really want to understand what's there at Mars and not see the stuff we brought with us by accident.

I think it will help to bring this home to the reader to tell a short story through possible future news stories that we might read if we do send humans to Mars.

This is fiction, but I do think that there is a distinct possibility that this could be a real future. It is consistent with our best current understanding of Mars.


Skip to: Yes we would love to touch Mars in person, but should we?

(based on the section of my Touch Mars? online book: Prestige or dishonour, first footsteps on Mars)

First Astronauts on Mars

The first astronauts to land on Mars plant flags in the soil

Photo shows Artist's impression of a human astronaut on the Mars surface holding Oskar Pernefeldt's proposed International Flag of the Earth

This would be so exciting for enthusiasts - the first astronaut on the red planet. We all cheer.

If it was an international expedition, as it would likely be because of the expense, I can imagine they might bring the “Flag of Earth” along with the other flags to show they come for all mankind.

Title: Mars Astronauts find Life!

Today Paul Maldonado, the astrobiology mission specialist, announced that he had found clear signs of life on Mars. The life was found in a Recurrent Slope Lineae close to their base camp.

(Photo is actually of a slope with RSLs from this paper)

Wonderful. What we have been looking for all this time. Also though I don’t say it in this short article - they might well gene sequence it, find it has the same genetic code as DNA, and announce that it doesn’t match any known Earth microbe.

This would be so exciting - except perhaps for some doubts amongst knowledgeable astrobiologists who would be somewhat dreading what comes next, after all this is what that long running debate in Astrobiology journal from 2013 to 2019 was all about.

If this happens and some of the astrobiologists seem a little subdued and not as excited as you’d think, this would be the reason:

Title: Big Disappointment - “Mars Life” was from Earth!

On close examination the life turns out to be a salt loving microbe that sneaked in on the spaceship with the astronauts themselves. It must have got blown in the dust storm that enveloped the camp soon after they got to Mars.

(Uses artwork by Dmytr0 from wikipedia)

Oh how sad. It was just an Earth microbe that snuck along for the ride as a hijacker.

It would be easier to make this mistake than you’d think. Our spacecraft are likely to have microbes that can survive on Mars. Spacecraft assembly rooms have a wide range of extremophile species.

The microbes carried by humans can have hidden extremophile capabilities - because microbes do not lose their capabilities, usually, when they move to a different environment. Some are polyextremophiles able to live in a variety of extreme environments as well as in much more ordinary ones (for humans).

A typical human has 100 trillion microbes in 10,000 species - and the species mix varies from one person to another. We have those extremophiles on our skins, in our clothes, for instance a recent study of microbial populations of human belly buttons found a couple of species able to thrive in extreme cold and extreme heat.

About half the species in our gut, even today, in 2019, are likely to be unknown to science. They can’t be cultivated yet outside of the human gut, and not for lack of trying. See Uncovering uncultivated microbes in the human gut and paper New insights from uncultivated genomes of the global human gut microbiome

It’s well possible that we bring along microbes that can survive on Mars and that we haven’t yet cultivated or sequenced. It depends how warm the habitat is - that’s the upside. Earth microbes do continue to grow even at very low temperatures but they get slower and slower, eventually reproducing every century and possibly at colder temperatures on timescales of millennia.

So, what about the dust? This is another point the 2015 review brought up that they felt wasn’t covered adequately in the 2024 report, terrestrial contamination blown in the Martian dust.

They agreed with the 2014 report that life would be strongly sterilized by the UV radiation - but some microbes are able to withstand it for up to several hours of direct martian sunlight. Also the life can form cell chains, clumps or aggregates and the cells in the interior of those aggregates would be protected.

The review said that research so far (as of 2015) was not sufficient to answer the question. The possibility of microbial contamination spread in the dust could be confirmed or rejected in terrestrial Mars simulation chambers.[44]

Well, that confirmation or rejection hasn’t happened yet as far as I know. On going research but it is not easy to duplicate the conditions of a Martian dust storm in a laboratory - and then - there are many unknowns about the dust too.

The dust would have perchlorates in it, but though hazardous to human thyroid glands, some microbes that use them as food and they are less reactive at low temperatures.

The UV light can convert these perchlorates to the more toxic chlorites and hypochlorites, but biofilms and hardy spores can resist those too, as might extremophiles. Also, less than a mm of dust can block out the UV light.

I go into that in this section of my preprint, just summarizing current research again:

UV tolerance by extremophiles and transport of spores in martian dust storms

The martian dust is as fine as cigarette dust and wherever the astronauts walk or their rovers travel they would kick it up. The Apollo astronauts got filthy with dust - well - Mars astronauts would be much dustier. The lunar rover threw up dust wherever it went but it just arced over in parabolas back to the ground again in the lunar vacuum. A Martian rover would create clouds of fine dust that would just hang in the air like the dust from a dust storm which takes a long time to settle.

Then the ground is typically covered in boulders, and the shadows of those boulders are protected from UV light, also the astronauts could just trample the spores into their footprints.

Mars has frequent dust storms and sometimes they go global. The Mariner 3 probe flew past Mars during a global dust storm. These typically start in the southern hemisphere, during the southern spring or summer, encircle the planet in southern latitudes then extend north across the equator and can cover much of the planet. (see page 129 of this article) (though unusually the 2018 one started in the northern hemisphere).

The dust travels hundreds of kilometers a day and can circle the entire planet in a week. The 2018 dust storm, for instance, grew all the way to a planet encircling dust storm in two weeks

So the microbes from a human base could end up anywhere on Mars.

It’s a rather similar situation in the McMurdo cold dry valleys in Antarctica (kept dry by the strong winds blowing off the continent).

The researchers there are interested in studying microbial communities - and rather like for Mars, they want to study the indigenous microbes rather than the ones they bring along themselves. The researchers stay within a fixed area around the camp in order to limit their impact, in a "corral" system.

This shows a typical Antarctic dry valley field camp. It's perhaps the closest biological analogy we have to a Mars base

Typical example, a corral that's 50 meters square.

After a ten day camp restricted to those 50 square meters, they will leave an estimated sixty billion microbes in the soil.

Assuming those sixty billion microbes are evenly mixed into the top one cm of the site, then that makes it around a hundred thousand microbes in each cubic centimeter, which is between 0.1% and 10% of the natural population of microbes in those sites. Calculations from page 4 of this paper: Non-indigenous microorganisms in the Antarctic: Assessing the risks

So there will be lots of microbes in the dust around a human camp on Mars. It would surely not be possible to keep them within the habitats - spacesuits leak air all the time for instance, so that they can move their arms. They would be taking equipment in and out of the habitat too.

While if a spaceship crashes like the Challenger - always a risk with especially the way Elon Musk plans to land there with supersonic retropropulsion which needs it to fly close to the ground. Possibly so low it has to fly below the walls of the Valles Marineres to get enough air resistance to stop. See Supersonic retropropulsion - or huge parachutes

The astrobiologists when they discuss this just assume that a human base will leak microbes and I haven’t seen any suggestion that there is any way to stop this.

Title: Native Mars Life Found - But Doomed to Extinction

The astronauts have found native life in the RSL. It contains RNA and ribozymes, but no DNA, ribosomes, or proteins, and is thought to be an “RNA world lifeform” that is more primitive than Earth life. It is no match for Earth life, which is expected to make it extinct.

Photo is of nanobes from "New life form may be a great find of the century" (1999), at one time thought to be relic RNA world life here on Earth)

This is based on the idea of a Shadow Biosphere which was quite a popular idea a few years back. It was a possible explanation of those nanobe structures. Modern DNA based life in its present form is far too complex to have arisen in one go. As for what came first, there are numerous ideas,and the RNA world hypothesis is one of them.

They had no success finding any RNA world life on Earth. But could it exist on Mars? Perhaps its there alongside Earth life, or perhaps it’s the only life there.

We have no idea what we’ll find on Mars and you can argue either way. Perhaps it has continued to evolve at a similar pace to Earth life or faster, and is as advanced as Earth life or more so. Or perhaps it has hardly evolved at all, because of the small population sizes and harsh conditions.

I made it RNA world life for the purposes of the story but it could be any form of early life that predates the Last Universal Common Ancestor (LUCA).

It’s not implausible for Martian life. This was one of the ideas for the structures in ALH84001, that they might be these RNA world cells. It was originally suggested by the fourth panel in Size Limits of Very Small Microorganisms (1999) - which was convened shortly after the martian life announcements. Although other possible explanations are known, enough so that those structures can’t be claimed as a “discovery of life”, the research hasn't disproved it either, they are just alternative explanations.

The jury is still out on whether the structures in ALH84001 were the result of life or not. In "Towards a Theory of Life" in the book "Frontiers of Astrobiology" (2012, CUP) by Steven A. Benner (notable as the first person to synthesize a gene) and Paul Davies, the authors talk about RNA world cells as a possible explanation of the structures. Early life based on those ideas could have had cells as small as 50 nm across.

"Why should proteins be universally necessary components of life? Could it be that Martian life has no proteins?

... Life forms in the putative RNA world (by definition) survived without encoded proteins and the ribosomes needed to assemble them. ... If those structures represent a trace of an ancient RNA world on Mars, they would not need to be large enough to accommodate ribosomes. The shapes in meteorite ALH84001 just might be fossil organisms from a Martian "RNA world".

The cells could be far smaller if they use ribozymes, made up of RNA fragments instead of the more complex ribosomes that mix protein with RNA. They could also have only single strand RNA based replication and none of the complex translation machinery to translate double strand DNA into RNA (including unzipping the DNA, and zipping it up etc).

This would make the cells far simpler and smaller than for modern life. Complex in what they do, in their capabilities - they would surely have dormant states to survive desiccation, and ways to combat the ionizing radiation, temperature changes etc, but perhaps that is all done with RNA.

Whatever the earliest forms of life were, it’s impossible that the complexity of modern life could arise in one go, with its thousands of different chemicals needed for even the minimum size of cell. Some simpler form must have arisen first, and perhaps is still there on Mars.

Whether those are fossils of life or not, as Harry McSween put it in an early paper in 1997

"this controversy continues to help define strategies and sharpen tools that will be required for a Mars exploration program focused on the search for life.

So I am supposing that they do find RNA world life. Though it doesn’t say, probably they found the RNA world life by drilling below the surface to a layer not contaminated by Earth life yet.

This early life could be very vulnerable.

To quote from my own biosphere collisions preprint again (summarizing existing research):

According to one idea, the earliest life, all the way through to the last universal common ancestor (LUCA), might have been simple “modifiable cells” capable of taking up “naked” genetic material and evolving through lateral transfer, by Lamarckian rather than Darwinian evolution (Woese, 2002) (Brown, 2003) (Jheeta, 2013).

Such life might, though primitive, yet be adapted to Mars. It may be the most perfectly adapted RNA world “modifiable cells” imaginable, with many specialist enzymes and other adaptations to help it to function in its extreme environment. Yet, such life might have little by way of defences against modern Earth microbes. Evolving through massively parallel Lamarckian evolution, easy and fast uptake of capabilities from its neighbours is the priority.

Although cells themselves would not yet be in competition with each other, the genomes within them would be. These might evolve some degree of genomic protection, in small vesicles. As described by Koonin:

"Conceivably, such primitive units of evolution could have been represented by small, virus-like replicons that populated abiogenic lipid vesicles or inorganic compartments and were subject to selection for replication efficiency" (Koonin, 2014)

If so, they eventually developed the complexity of a cell and at that point the first steps in true Darwinian evolution would have begun. However, on Earth, this first stage may not have happened until as late as 3.5 - 3.8 billion years ago (Doolittle, 2000). If so, our Earth could have had several hundred million years of evolution before the transition to Darwinian evolution.

Potential Severe Effects of a Biosphere Collision and Planetary Protection Implications

That then would take us to the end of the Noachian period on Mars, when it still had abundant water and seas.

Perhaps what we have there are still replicons in undistinguished cells that share their genetic material with each other readily. You can imagine such simple life being vulnerable to our life. Something must have made it extinct on Earth and if whatever did that hasn’t got to Mars yet, we could easily be the vehicle that brings it to Mars, whether predation or competition with cells with a more efficient metabolism, or bacteriophages (if sufficiently related) or whatever it is.

Even if there is Earth life there, the early life might be there too in a shadow biosphere,(Cleland, 2007),

Also there’s another possibility, based on Charles Cockell's work on “Trajectories of martian habitability” (Cockell, 2014).

Mars at the moment is reasonably habitable - at times it’s been more so, but at times in the past less so. Maybe the surface life gets a reset from time to time when it goes extinct (perhaps with other life existing deep down all the way through).

If so, perhaps life has evolved again, starting a few tens of millions of years ago, It could then be at a very early stage of evolution.

From my preprint again:

If we are clumsy, could this invasion of Earth life continue rapidly to the extent that before we have the opportunity to study it thoroughly, or learn how to cultivate it, nothing remains of the native life of Mars, Europa or Enceladus, even in a shadow biosphere? Or if anything remains, only as capabilities transferred from the native life into Earth microbes?

Potential Severe Effects of a Biosphere Collision and Planetary Protection Implications

Title: Astronauts Regret Making Mars Life Extinct

Experts say that it is too late to do anything about the introduced Earth life on Mars since the dust storms will spread their spores, and dormant microbes, throughout the planet. The astronauts say that they regret making the native Mars life extinct. Can we do anything to protect at least some of the RNA world life on Mars? So far there has been no success in getting it to replicate in the laboratory.

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

Though the martian life is perfectly adapted to Mars, it doesn’t mean it is going to be easy to grow in the laboratory. After all our best studied microbiomes such as the human gut still have many uncultivated microbes and that’s after decades of trying.

The unique physical and chemical conditions on the Mars surface might be hard to replicate in the laboratory and the microbes that were collected might depend on others in a community, maybe they didn’t manage to collect the pioneer microbes able to colonize a habitat initially (or maybe that is a slow process that we can’t replicate easily in the lab).

They might well die on the journey back to Earth as the astronauts struggle to keep them alive but fail, especially if it is an early pre-LUCA form of life with no defences against Earth life. Then maybe with the next visit to Mars that early life can’t be found any more and is now extinct. It might have been a last relict of an ancient biosphere.

Few science fiction authors have tackled the theme of forward contamination of other parts of our solar system by Earth microbes, but there's one poignant sad story, by Arthur C. Clarke, "Before Eden", in Amazing Stories, June 1961. Back then, though they knew Venus was hot, scientists thought it was still possible that Venus could have water on its surface, perhaps at the top of its mountains.

One of the covers for Arthur C. Clarke's "Before Eden" -a poignant sad story about forward contamination of Venus, published in 1961 at a time when surface life there was still a remote scientific possibility. You can hear the complete story read as an audio book here.

These adventurers are exploring a completely dry Venus, or so they think. Up to then (in the story), everyone thought Venus had no water, and was sterile of life. That was a natural thought, because the temperatures they encountered were always above the boiling point of water. But the heroes of the story are stranded near the not quite so hot South pole, and find mountainous cliffs there. On those mountains they find a dried up waterfall - and then - a lake!

“Yet for all this, it was a miracle—the first free water that men had ever found on Venus. Hutchins was already on his knees, almost in an attitude of prayer. But he was only collecting drops of the precious liquid to examine through his pocket microscope.... He sealed a test tube and placed it in his collecting bag, as tenderly as any prospector who had just found a nugget laced with gold. It might be – it probably was – nothing more than plain water. But it might also be a universe of unknown, living creatures on the first stage of their billion-year journey to intelligence....”

“...What they were watching was a dark tide, a crawling carpet, sweeping slowly but inexorably toward them over the top of the ridge. The moment of sheer, unreasoning panic lasted, mercifully, no more than a few seconds. Garfield’s first terror began to fade as soon as he recognised its cause....”

“… But whatever this tide might be, it was moving too slowly to be a real danger, unless it cut off their line of retreat. Hutchins was staring at it intently through their only pair of binoculars; he was the biologist, and he was holding his ground. No point in making a fool of myself, thought Jerry, by running like a scalded cat, if it isn’t necessary. ‘For heaven’s sake,’ he said at last, when the moving carpet was only a hundred yards away and Hutchins had not uttered a word or stirred a muscle. ‘What is it?’ Hutchins slowly unfroze, like a statue coming to life. ‘Sorry,’ he said. ‘I’d forgotten all about you. It’s a plant, of course. At least, I suppose we’d better call it that.’ ‘But it’s moving! ’ ‘Why should that surprise you? So do terrestrial plants. Ever seen speeded-up movies of ivy in action?’ ‘That still stays in one place – it doesn’t crawl all over the landscape.’ ”

“‘Then what about the plankton plants of the sea? They can swim when they have to.’ Jerry gave up; in any case, the approaching wonder had robbed him of words... ”

“... ‘Let’s see how it reacts to light,’ said Hutchins. He switched on his chest lamp, and the green auroral glow was instantly banished by the flood of pure white radiance. Until Man had come to this planet, no white light had ever shone upon the surface of Venus, even by day. As in the seas of Earth, there was only a green twilight, deepening slowly to utter darkness. The transformation was so stunning that neither man could check a cry of astonishment. Gone in a flash was the deep, sombre black of the thickpiled velvet carpet at their feet. Instead, as far as their lights carried, lay a blazing pattern of glorious, vivid reds, laced with streaks of gold. No Persian prince could ever have commanded so opulent a tapestry from his weavers, yet this was the accidental product of biological forces. Indeed, until they had switched on their floods, these superb colours had not even existed, and they would vanish once more when the alien light of Earth ceased to conjure them into being...”

“...For the first time, as they relaxed inside their tiny plastic hemisphere, the true wonder and importance of the discovery forced itself upon their minds. This world around them was no longer the same; Venus was no longer dead – it had joined Earth and Mars. For life called to life, across the gulfs of space. Everything that grew or moved upon the face of any planet was a portent, a promise that Man was not alone in this universe of blazing suns and swirling nebulae. If as yet he had found no companions with whom he could speak, that was only to be expected, for the lightyears and the ages still stretched before him, waiting to be explored. Meanwhile, he must guard and cherish the life he found, whether it be upon Earth or Mars or Venus. So Graham Hutchins, the happiest biologist in the solar system, told himself as he helped Garfield collect their refuse and seal it into a plastic disposal bag. When they deflated the tent and started on the homeward journey, there was no sign of the creature they had been examining. That was just as well; they might have been tempted to linger for more experiments, and already it was getting uncomfortably close to their deadline. No matter; in a few months they would be back with a team of assistants, far more adequately equipped and with the eyes of the world upon them. Evolution had laboured for a billion years to make this meeting possible; it could wait a little longer.”

“...For a while nothing moved in the greenly glimmering, fog-bound landscape; it was deserted by man and crimson carpet alike. Then, flowing over the wind-carved hills, the creature reappeared. Or perhaps it was another of the same strange species; no one would ever know. It flowed past the little cairn of stones where Hutchins and Garfield had buried their wastes. And then it stopped. It was not puzzled, for it had no mind. But the chemical urges that drove it relentlessly over the polar plateau were crying: Here, here! Somewhere close at hand was the most precious of all the foods it needed – phosphorous, the element without which the spark of life could never ignite...”

" ... And then it feasted, on food more concentrated than any it had ever known. It absorbed the carbohydrates and the proteins and the phosphates, the nicotine from the cigarette ends, the cellulose from the paper cups and spoons. All these it broke down and assimilated into its strange body, without difficulty and without harm. Likewise it absorbed a whole microcosm of living creatures—the bacteria and viruses which, on an older planet, had evolved into a thousand deadly strains. Though only a very few could survive in this heat and this atmosphere, they were sufficient. As the carpet crawled back to the lake, it carried contagion to all its world. Even as the Morning Star set its course for her distant home, Venus was dying. The films and photographs and specimens that Hutchins was carrying in triumph were more precious even than he knew. They were the only record that would ever exist of life’s third attempt to gain a foothold in the solar system. Beneath the clouds of Venus, the story of Creation was ended.”

How sad it would be if future explorers on Mars get glimpses of early forms of life on Mars, and then they go extinct soon after they are discovered. Or indeed, even before, maybe they are extinct before anyone finds them. It would be great to be able to say that humans on Mars will cause no problems. It's what most of us want to be true, and we love to read science fiction stories, and watch movies, based on this idea. If you say this, you are bound to be popular with space colonization enthusiasts and science fiction geeks, and your work will probably get widely shared.

But our actions on Mars will have real world consequences, and won't just lead to popular acclaim and book or movie sequels. We don't get to write the script for what happens next. We need to take a careful and thorough look at what might actually happen before we act. Let's look beyond the widely shared optimistic stories reassuring us that nothing can go wrong.

The last few paras here are from my:


I don’t think Elon Musk would want to do this, or Robert Zubrin, or most space colonization enthusiasts, and for sure NASA don’t. The main risk here is that someone in private space, makes an executive decision that he is not risking extinction of Martian life, or NASA does, and makes the wrong call.

That’s especially concerning because it seems from the way this report was handled that the decision may devolve to planetary geologists and colonization enthusiasts rather than to astrobiologists. However an astrobiologist might also make the wrong decision here, out of enthusiasm for space settlement and space colonization. We should base such decisions on the full range of views of astrobiologists and not just those that make the decision we like.

So then we get the last of this series of poignant sad news stories from this (hopefully alternate) future where the first astronauts to land on Mars make native Martian life extinct.

The Lascaux cave painting photo is by Prof Saxx.

I made these “Future Possible News” stories with this online spoof newspaper generator. I invented the name of the astrobiology mission specialist using this online fake name generator.

I go into this analogy in my Touch Mars? book.


Skip to: So what do we do? - To the Moon!

Here I'm quoting from the section: Touching Mars in my Okay to Touch Mars? online book.

We love to touch things. If you put a sculpture in an art gallery and say "please touch", you can guarantee it, that both children and adults will do so. So it's natural that we want to touch Mars too, and other planets, if we can.

However, there are plenty of things we can't touch on Earth. It’s not just that you might want to touch a Van Gogh painting, say, to feel the texture of the paint. Not just to touch sculptures and works of art in art galleries. The Lascaux cave paintings for one,

Photograph of the Lascaux paintings by Prof Saxx.

Many of us would love to touch these paintings, as the original painters did, and feel the texture of the rock they are painted over. But not only are we not permitted to touch them - we have to take care even about going into caves like these at all.

The warmth, humidity and carbon dioxide from our breath have taken their toll. Fungi and black mold are attacking the ancient cave paintings.

The purple markings in this photograph show some of the damage we've caused, not directly, but through our breath and in other ways, unintentionally.

The cave was found by four children, out with their dog in the 1940s after a tree blew down exposing a hole in the ground. It was opened to the public immediately after WWII, when the owners of the land, the La Rochefoucauld family, enlarged the entrance, added steps and replaced the sediment that covered the cave floor with concrete. This venture was wildly successful, with 1,500 visitors a day, but the humidity, carbon dioxide and warmth of all the visitors took their toll.

This lead to microbes, fungi and black mold colonizing the cave. They eventually closed down the cave and made a copy of it for the visitors, known as Lascaux II, recreated using the same techniques and pigments, as best they could. Only specialists can visit the original now, but it is already too late to restore it back completely to its original condition.

Scientists have often made things worse as we try to fix them, with one more misstep after another. For instance, after a white fungus spread over the floor and up the walls, the scientists took great care to photograph every single painting in detail, to keep track of the damage. It seemed an eminently sensible thing to do.

What they didn't realize is that the bright lights they needed for their photographs were damaging the cave paintings, by encouraging the growth of a black mold. This is now a major issue there with black spots spreading over the paintings.

For details see the Washington Post article: Debate Over Moldy Cave Art Is a Tale of Human Missteps.

In a recent conference, climatologists said that it is possible to restore the original environmental conditions of the cave. But the microbiologists said that it is not possible to restore the pre year 2000 microbial conditions. They say that the only way forward is to just accept that we can't do anything about the new species of microbes we've brought there. Instead, we have to try to find a new equilibrium. Trying to destroy the new invasive microbes will only make things worse.

If we can’t restore the original microbial conditions inside the Lascaux cave - how can we hope to restore the original microbial conditions on Mars after introducing Earth life there? Clearly we can’t.

We need to know it is what we want to do, or, just as for the Lascaux caves, the next generation will not be able to explore Mars as it is today, and there may be numerous treasures there, biological treasures, that we may put out of reach for them.


Skip to: We have plenty of time before humans get to Mars

Well first, this scenario I think is much further into the future than NASA or Elon Musk seem to think.

The retired Canadian astronaut Chris Hadfield, former commander of the ISS, interviewed by New Scientist, put it like this in their article "We should live on the moon before a trip to Mars"

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

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

By a generation I take him to mean that the babies being born today would be the young astronauts that could go to Mars orbit - probably some time in the 2040s.

I think that Mars often seems more hospitable than it is because of the sky, a kind of golden brown - but often even colour adjusted to blue.

If you add a blue sky to the lunar photos it suddenly looks far more hospitable.

These images are not altered in any way. All I've done is to crop them, and replace the black skies with photographs of blue skies and clouds from Earth.

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

Actually if you examine it carefully, the Moon has many advantages over Mars. I was surprised and didn’t expect this when working on my Case for Moon first.

The vacuum is actually a benefit over Mars. It lets you do direct vapour deposition of solar panels, for instance, with a harder vacuum than our best factories on Earth. It means the iron in the dust is the pure metal and not oxidized - the rather appealing rusty red of Mars is actually a sign it is less useful than the lunar dark material which has pure iron in it.

It has twice the amount of sunlight for solar power, and not only that - at the lunar poles there are regions with solar power almost year round, 24/7. There is nowhere like that on Mars, not only that, the

The CO2 in the Mars atmosphere is not much use for humans, as CO2 is normally a waste gas you are trying to recycle as much as possible. If the system is fully recycling then it gets taken up again by plants and you eat it again in your food but if the colony imports any food from Earth it will have a CO2 excess.

The pressure level on Mars is nowhere near enough to let you use only scuba gear, but have to use a full pressure spacesuit. The dust on Mars is laced with perchlorates, and possibly chlorates and chlorites through UV. Although the lunar dust is sharp edged it hasn’t got any chemical nasties. Either way you want to keep the dust out.

Then - the lunar rovers sprayed dust wherever they went

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

On Mars they would surely do the same, but the fine dust, as fine as cigarette dust, would just hang even in the thin atmosphere, as we see with the Martian dust storms.

Imagine this rover driving around on Mars with the dust just hanging in the air wherever it goes:

(click to watch on Youtube)

As I say in my preface to Case for Moon first:

You may have heard advocates say we should ignore the Moon, and head straight for Mars, and they may even say that the Moon is as dull as a ball of concrete. But what about the other view, put forward by many enthusiasts for the Moon, that we should start there instead,as the first place to send humans after LEO? As you read this book, you may be surprised to learn that the Moon is resource rich, and fascinating, with many new discoveries since the time of Apollo, as well as many mysteries still to solve. It may have potential for exports of metals and volatiles. It's also far more promising for tourist hotels, and human research stations, because it is so much easier to get to than Mars, it's a great place for radio and infrared telescopes, and it's potentially valuable as a place to make computer chips and solar cells that require high vacuum, amongst other benefits. And it may surprise you a lot to learn that the Moon has many advantages over Mars as a place to create habitats for humans too.

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

For more on all this see my Case For Moon First


skip to Earth has strong legal protection

I don’t think Musk or anyone else will have these large Starships flying for a few years yet. Elon time as they call it. Suppose he has them flying to the Moon by 2025.

Well - to head off to Mars at that point is like Chris Hadfield’s

'We’ve got boats, we’ve got paddles, let’s go to Australia!'

Okay they fly, they have life support - but - suppose as your mission leaves Earth, it has an explosion as for Apollo 13, or a chemical release, or fire, or a failure of the life support, or breach of the hull.

If this was a nuclear sub, say, you could have some hope of getting to the surface and being rescued. But there is no oxygen around for millions of miles, no water, just the vacuum of space. No med vac, no dinghies. We simply don’t have any situation like that on Earth where people are so isolated not just from support from other humans, but from any nature services or resources or habitability.

If the enthusiasts think they are ready to go to Mars, well, let’s do a mission to the far side of the Moon. Study it from the L2 position via telepresence. Simulate the time delay for radio signals to Earth. Leave a crew there for two years with no resupply from Earth and not permitted to return except in an emergency.

If they can do that, then they may be ready to do a Mars flyby in an armada of three for safety, maybe three spaceships with triply redundant everything. However most likely something goes wrong. I’d be surprised if we are ready to go to Mars in less than a decade after the first landings on the Moon by this Starship.


skip to How Extraterrestrial microbes could be hazardous to humans or Earth's environment

In the backwards direction from Mars to Earth, we are strongly protected by many environmental laws and laws to protect human health that we didn’t have at the time of Apollo. These laws don’t rely on the Outer Space Treaty for their legal basis. How NASA categorizes Mars makes no difference to them. See the article by Margaret Race of the SETI institute.

NASA is going to send a sample caching rover to Mars in 2020 and they hope to send a second mission in the 2020s to return some of these samples back to Earth for analysis. They plan to return them unsterilized (a sterilized sample would not trigger environmental laws, but would be just like the sample returns from meteorites, comets, and the Moon). Their current plans are to return it in 2032.

NASA have put a great deal of work into the engineering for a sample return but I can't find any papers or blog posts or any sign of prepration for the legal side of the return mission.

I tried to estimate a timetable for the legislation, based on Margaret Race's article. Assuming the process goes through with no hold ups or objections, they probably should have started in 2010 or earlier if they want a sample return by 2032. If you know of anything on this do say in the comments.

These laws don't depend on the wording of the Outer Space Treaty in any form, but are independent legislation to protect Earth.

Text: NASA have left it too late to complete the legal process for a 2032 unsterilized sample return. They should have started around 2010.

Mars sample return concept - credit NASA. If NASA wants to return an unsterilized sample by 2030 they should have started the legal preparation for this around 2010 at the latest. There is no sign they have even done any planning for the legal process yet.

Perhaps they expect it to be like Apollo 11 where they published the sample return precautions as an informal document on the day of the launch to the Moon and didn’t go through any proper legal process? This would not be permitted today.

This takes into account the likely time requirements for constructing the receiving facility, based on the previous sample return studies. NASA would not start the expensive build (half a billion dollars facility) until it knows what it is legally required to do. I did this calculation back in 2018 for my article: Why we are unlikely to return an unsterilized sample before 2040. Let's look at it again:

The requirements for a sample return facility have increased with each review. In 1999 then they recommended use of Class III Bio Safety Cabinets (BSC's) in combination with HEPA filters. This was still the general idea in 2002. They described the facility like this:

"The initial processing of returned martian samples should be restricted to a BSL-4 laboratory in the quarantine facility. A very modest gas-tight glove box (Class III cabinet) in a "clean room" (class 10; however see following g section) will be sufficient for this purpose. "

These requirements were made increasingly more stringent as a result of the discoveries of ultramicrobacteria, the studies of the minimal possible size of extraterrestrial microbes (thought to be around 50 nanometers, a quarter of the minimum size for modern Earth life) and the discovery of how easily capabilities can be transferred through lateral gene transfer, to the most distantly related microbes. It's now thought that even distant cousins on Mars, separated from Earth life for billions of years, could easily swap genes with Earth life overnight in warm salty brines such as sea water. Even if they were dead. Even if particles only a few tens of nanometers in size from martian life got into the sea that could still be enough to transfer a capability to Earth life.

The most recent study by the European Space Foundation required a $500 million facility with design requirements never fulfilled before that has to prevent escape of any particle of 50 nanometers diameter or more (a quarter of the resolution limit of 200 nm for a diffraction limited optical microscope) under any circumstances. They leave it for further discussion whether a 10 nm particle can escape from the facility, recommending that they also should be contained, and that if this is not practical, that the situation needs to be reviewed. These are extraordinarily demanding requirements, especially when you combine them with the requirement to keep the martian life uncontaminated by Earth life so that it can be studied.

For a summary of their conclusions with links to the sources, see

It's perhaps not surprising, however, that the process is so complex and difficult. What makes it such a challenge is that we have to contain any conceivable extraterrestrial biology, when so far, we only have knowledge of Earth based life. We would build the same facility to receive an unsterilized sample from a habitat in the Proxima Centauri system!

The most recent European Science Foundation - study. was in 2010, and a sample return mission launched in the 2020s would likely need a new study. This is not likely to reduce these requirements, but instead would be expected to increase the requirements further, at least each previous study has done so. Then the law, whatever it is, would be likely to be based on their recommendations, after much deliberation during which the public would be involved at every stage in a full and open way.

The recommendations so far are that the facility also has to be operational and in use at least two years before the mission to collect the sample is launched from Earth. This requirement is the result of studying the many lapses of protocol during the Apollo mission sample handling, due to staff that were not sufficiently familiar with the procedures. For details of these lapses see When Biospheres Collide, A History of NASA's Planetary Protection Programs ..

However the National Research Council study in 2009 estimated a longer period of 7 to 10 years to get operational, followed by an estimated 5-6 years to become familiar with the procedures

It has been estimated that the planning, design, site selection, environmental reviews, approvals, construction, commissioning, and pre-testing of a proposed SRF will occur 7 to 10 years before actual operations begin. In addition, 5 to 6 years will likely be required for refinement and maturation of SRF-associated technologies for safely containing and handling samples to avoid contamination and to further develop and refine biohazard-test protocols. Many of the capabilities and technologies will either be entirely new or will be required to meet the unusual challenges of integration into an overall (end-to-end) Mars sample return program.

Timescale for establishing a sample-receiving facility

It is not likely that the process of designing and building the facility would start until the legal provisions are in place with the details of the design requirements.

Margaret Race looked in detail at the legal processes that would have to be completed before we can return a sample from Mars to Earth, even to a purpose built receiving facility.

Before a sample return, we have to accomplish, in this order

  • Several years: Formal environment impact statement for NEPA + laws on quarantine to be enacted, involving broad public consultation. The average length of time for an EIS in the twelve months ending 30th September 2016 was 46 months (see the DOE's Lessons Learned Quarterly Report).
  • Several years: Presidential review of potential large scale effects on the environment. This has to be done after all the other domestic legislation is completed.
  • Can be done alongside the other work: International treaties to be negotiated and domestic laws of other countries

I have only mentioned a few of the main points there.

In more detail, summary of Margaret Race's findings:

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

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

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

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

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

Margaret Race does not estimate a total time for all this. But we need a figure to work with here, so let's say, as a a rough estimate, that a decade would seem optimistic to complete it all.

Once the legal situation is sorted out and the design requirements of the facility are required the next steps are:

  • 7 - 10 years: building the facility
  • 2 years: operational before launch (minimum requirement, more likely 5-6 years)
  • 2 - 4 years: to collect the sample and return it
    (if we follow the Mars 2020 plan then the follow up rover has to retrace at least part of the path of Mars 2020 to retrieve the samples, in tubes that are dropped on the surface of Mars in small caches from time to time).

That add up to an extra 11 - 20 years after the legal process has completed. Total 21 to 30 years. The process of building and testing the facility alone could take 20 years if we go by the upper estimates there. Do say in the comments if you see anything to correct in this estimate of the timescale.

If this calculation is correct, this means that if we want a sample returned to Earth by 2032 we should have started this process already in 2010. Indeed, it is probably already a year or two too late to achieve a sample return date of 2040. Also, this assumes that there are no delays. It would be no great surprise if it was delayed to 2050 or later through either legal delays or delays in building the facility and getting it operational.

If anyone reading this knows of any work NASA has done by way of preparing for the legal situation do say. I have searched and found nothing and with my previous articles I've asked readers to comment and asked knowledgeable friends, and not found anyone who knows of anything they have done on this topic or are doing on this topic.


Skip to: Any humans to Mars would be one way unless we know Mars is safe

Of course if they could prove Mars is sterile, or that any martian life is harmless to Earth, then this would not be needed. However, at least with the current state of knowledge of Mars, astrobiologists would tell the legislators that Mars could have extraterrestrial life there. It’s not known to be sterile, and the dust can carry spores almost anywhere on the planet (more on this later). Over the years of legal process, this would be looked into in great detail from all angles.

As we’ll see new discoveries have opened up the possibility of native microbial life on Mars hidden from our orbital telescopes just centimeters below the dust. This may be possible even in the exceedingly dry tropical areas where Curiosity is roving, especially if martian life has a biochemistry adapted to lower temperatures than Earth life.

This life could be hazardous to humans or our biosphere. To take a simple example, legionnaires disease is an infection of biofilms that can use the same methods to infect human lungs, seeing it as a warm biofilm - it is not adapted to humans. Some strains of it are now adapting to our environments, spread by humans infected by it, but the same could happen with Martian life that invades the lungs of an astronaut.

Astrobiologists say that though it is possible that Mars life could be mystified by an alien biochemistry, it’s also possible that it hasn’t evolved any resistance to it, never having encountered it before. Joshua Lederberg put it like this:

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

from: "Paradoxes of the Host-Parasite Relationship"

Our lungs might offer no resistance, not even recognizing it as life as it munches away at them, and with a different biochemistry they would be likely to be naturally resistant to our antibiotics, which target particular processes of the pathogens.

Some Mars colonization enthusiasts and space engineers will tell you that any life we find on Mars will be from Earth, but they have not persuaded the astrobiologists of this. The designers of instruments to look for indigenous life there are careful not to make any assumptions about its biochemistry or whether it is related to Earth life.

We can’t assume that any life in a sample returned from Mars is related to Earth life unless we have studied it already on Mars.

There would also be risk of larger scale environmental disruption, even if the martian microbes are harmless to humans. As the National Research Council put it in 2009:

The risks of environmental disruption resulting from the inadvertent contamination of Earth with putative martian microbes are still considered to be low. But since the risk cannot be demonstrated to be zero, due care and caution must be exercised in handling any martian materials returned to Earth

Assessment of Planetary Protection Requirements for Mars Sample Return Missions

These reports haven't gone into details of how the environment could be disrupted. To give some points to think over right away (I will come back to this later), would our ecosystems work the same way if eventually half the microbes in the soil, half the plankton in our oceans and half the microbes in the guts of animals and ourselves were mirror DNA, say, or PNA, or TNA, or had novel amino acids that Earth life doesn't use, or didn't use proteins, to give a few examples? How would Earth life respond to eating food with novel amino acids it never encountered before or with mirror versions of the amino acids it has already? What about accidental poisons, like the way that cyanobacteria can kill dogs and cows? This is especially so if the extraterrestrial microbes have a different biochemistry; they seem unlikely to be exact "drop in" replacements to terrestrial microbes. There would be changes in their composition and how they function. Microbes with their shorter lifespans would adapt relatively quickly, but higher lifeforms might find it a significant challenge.

The legislators would not ignore arguments such as these. There would be extensive public debate, and Earth would be protected.

Robert Zubrin (president of the Mars society) tells his space colonization enthusiasts that for Mars life to survive on Earth is like Sharks in the savannah (see What are Zubrin's arguments? in my Touch Mars? book). But they could also be like rabbits in Australia, and microbes aren't like sharks. Microbes able to thrive in extreme heat and extreme cold have been found in human belly buttons . You need to listen to astrobiologists, not space engineers, and for sure the legislators would listen to the astrobiologists. There is a reason why we protect Earth.

Yes, there are scenarios according to which martian life would be harmless to us. It could be that what we find on Mars is an early form of life, so feeble it can't compete with Earth life, or it's adapted to very low temperatures and self destructs when it is warmed up. You can invent other scenarios where martian life is harmless to Earth, or even beneficial in some way. However, before an unsterilized sample return, we will need much more by way of evidence than optimistic scenarios or colourful analogies. Legislators would invite the astrobiologist experts to give evidence, and would not ignore what they say.

For these reasons I’m not concerned about the backwards direction as far as safety is concerned. I expect NASA to sterilize their sample if they do return those samples from Mars to Earth, or return them to somewhere isolated from contact with Earth, such as a satellite set up for telerobotic study of the sample above GEO. They can use either of those approaches within the Outer Space Treaty. If there is no possibility of an unsterilized sample contacting Earth's biosphere, or Earth entering into the chain of contact with an unsterilized sample, it wouldn't trigger this legislation to protect our Earth.


Skip to: Why astrobiologists are not so keen on a sample return right now

I don’t see any humans that go to the Mars surface returning to Earth before 2040 or until we understand the Martian biochemistry in situ.

Hopefully also space colonization enthusiasts can come to see that these planetary protection requirements are not just pointless paperwork. It may seem like just a form of rubber stamping but it’s not.

The key to finding out if Mars is safe is to study it. But - not through a sample return. We need to study it in situ. A single mission returning samples of rocks from one area of Mars would not prove that Mars is safe for Earth. Indeed, it's hard to see how any number of sample returns could do that - unlike geology, you can't just test one rock, and expect all geologically similar rocks to be similar as regards astrobiology. The dust, salts, ices, are of special interest to astrobiology and there is only one way to find out if there is life there - to look in situ, and look everywhere.


Skip to: Colliding biospheres could be beneficial

Although not concerned about the safety issue for a sample return, I do think it is not the best of strategies from an astrobiological standpoint, because astrobiologists don't seem to be keen on a sample return at present, not until we first find life on Mars.

They think it is likely to return rocks not that different from the martian meteorites we have already. Indeed, our two most interesting Martian meteorites, ALH84001 and the Tissint meteorite would be marked as top priority targets to return from Mars. The context might give some useful information but they would be likely to be as inconclusive to astrobiology as the meteorites we already have. From their perspective, it seems like an extremely expensive way to possibly add some small fragments of meteorites to the ones we already have. Or, perhaps it is a demo mission for a future time when we might know what it is we want to return from Mars for the purposes of astrobiology.

The astrobiologists want to send life detection instruments to search for life in situ on Mars. Only after that, they would then look into sample returns.

I haven't found any recent papers by astrobiologists in favour of a sample return.

As Chris McKay put it, in this interview

If we’re going to search for life, let’s search for life. I’ve been saying this to the point of exhaustion in the Mars community. The geologists win hands down as they are entrenched in the Mars program...

...Right now, as far as I’m concerned, there is no alignment between the Mars strategy and astrobiology.

See my:

Astrobiologists arguing strongly for an in situ search on Mars first

Anyway there doesn't seem much one can do about this. NASA are set in this direction and it would take a lot to change it, with the rover built and ready to go.


Skip to: Possibility of hazardous life for astronauts on Mars

If you are optijmistic, it might be that humans, by going to Mars and shedding micro-organisms, just provide a wider range of habitats for martian life - and that in turn the martian life never harms us either but is only beneficial in its effects on Earth life too. Perhaps it may be a wonderful symbiosis of the two biospheres. For example, introduced lichens, if Mars has never evolved them, could provide habitat, shelter (from the UV) and food, as a prime producer, using just carbon dioxide, water vapour, and trace elements from the basalt. If Mars had lichens in the past and they went extinct, it could help through taxon substitution.

Schlaepfer et al did a survey of invasive species and in their table 1 they find many non native species that are actually beneficial. Some were deliberately introduced for their value for conservation. Many of the best examples were introduced unintentionally. Here are some of their categories.

  • Habitat, shelter, and food for native species (e.g. non native tamarisk as nesting sites for nesting birds, and non native plants in California for native butterflies to lay their eggs and for the caterpillars to feed).
  • Catalysts for restoration - e.g. non native guava trees in Kenya support fruit eating birds and encourage seed dispersal leading to forest restoration
  • Ecosystem engineers - e.g. non-native sea squirts (ascidian) in intertidal waters in Chile creating three dimensional matrix that increases species richness
  • Taxon substitution - e.g. Aldabra giant tortoise replacing extinct Cylindraspis giant tortoise in the Mascarene island (this one was intentional)

    The potential conservation value of non‐native species.

Perhaps non native life from Mars could benefit Earth ecosystems too in some way. For instance, it could, help challenged ecosystems to take up nitrogen more efficiently for instance (nitrogen is rare in the Martian atmosphere and it is just on the verge of possible for Earth microbes to fix it at those pressures, for a survey of the literature, see my section Sources of nitrogen - essential for life on Mars , in Okay to Touch Mars?: or my Sources of nitrogen on Mars in my preprint Potential Severe Effects of a Biosphere Collision).

But it could be harmful.


Skip to: Value of interesting indigenous martian life

Enthusiasts for humans on Mars should also care about making sure that it is a safe place for humans to land. If there is life there, they need to know what precautions to take.

Sometimes enthusiasts argue that martian life is not likely to be able to survive in human habitats because of the lack of oxygen, warmth etc. Robert Zubrin compares this with sharks trying to survive in the savannah.

However, it’s not so different as it seems. The surface of Mars is highly oxygenated with perchlorates, hydrogen peroxide, a small amount of oxygen in the air and potentially significant amounts in the brines, according to the work of Vlada Stamenković. This is an interview I did via email with him:

Also Earth is not likely to be too warm. Mars probably has hydrothermal vents, and so, at least some microbes that in the past have lived in very hot conditions and pre-adapted to live in such conditions. What’s more the surface is often well above zero degrees centigrade in the equatorial regions in daytime.

Until we know more it’s reasonable to suppose that Martian life is able to survive on Earth. Also, after returning it to Earth then over a period of time, if it is able to compete on equal terms with Earth life, it can spread and adapt perhaps to all or most of our ecosystems.

Would an ecosystem work the same way if half the microbes are Earth originated and half are martian life? If the martian life is based on a different biochemistry? Perhaps with perchlorates used internally instead of chlorides, and producing different chemicals that make sense on Mars but are unfamiliar with Earth life?

If it spread through Earth’s biospheres and most microbiomes became a mix of Earth and martian microbes, many or all higher life on Earth might not be adapted to coexist with these microbiomes with their alien chemistries (for instance their cells might well incorporate perchlorates instead of salts and chemical signals and toxins from an alien biochemistry). Toxic algal blooms in the Great Lakes kill dogs and cows that eat them, so for sure, alien life could harm us if it spread through our ecosystems.

From the example of legionnaires’ disease it could be harmful to humans directly too. Amongst other points, antibiotics would be likely to do nothing to stop life based on an alien biochemistry. After all, Earth microbes evolve resistance by using alternatives to the particular cell processes targeted by the antibiotics. Alien life, if based on a different biochemistry, would likely already use different cell processes from the ones targeted by the antibiotics. Our medicines would most likely offer no or little protection to us.

Also, there could be acidophiles on Mars as well. It’s likely to have acidic sulfate caves for instance. Martian life might perhaps be able to live in our guts too. Would our digestion system work the same way if half the microbes in our guts, eventually, originated on Mars?

So, it could be harmless, yes, but there is a distinct possibility that we find life on Mars that is hazardous to humans. It is because of this possibility that we are required to check it is safe before returning any to Earth.

The physicist Claudius Gros briefly describes the potential results of a clash of biospheres in his "Genesis project" to develop ecospheres on transiently habitable planets (see section 4.2 Biosphere compatibilities of this paper). Here, he makes an interesting additional point. Generally our biology only evolves defense mechanisms for a threat which is actually present, not just one that is a theoretical possibility that the life has never encountered.

If martian life is unrelated to Earth life, especially, then any threat it presents has so far only ever been a theoretical possibility as far as any Earth life is concerned.

He is using this argument for Earth life introduced to a foreign extraterrestrial biosphere, but you can equally apply it the other way around for martian life returned to Earth.

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

"In the best case scenario the microbes of one of the biospheres will eat at first through the higher multicellular organism of the other biosphere. Primitive multicellular organism may however survive the onslaught through a strategy involving rapid reproduction and adaption. ... "

"In the worst case scenario more or less all multicellular organism of the planet targeted for human settlement would be eradicated. The host planet would then be reduced to a microbial slush in a pre-cambrian state, with considerably prolonged recovery times. The leftovers of the terrestrial and the indigenous biospheres may coexist in the end in terms of ‘shadow biospheres’ "

If this is all accepted, it makes sense for the enthusiasts too to find out what is on the Mars surface before landing humans there.

It could be that it is totally harmless, or indeed beneficial. Or it could be harmful. We need to know.


Skip to: The spectacular HERRO telerobotics orbit

This may seem bad news to potential colonization enthusiasts. But if we can protect Mars and it has interesting indigenous life this would be a huge incentive to send humans there, to study it from orbit. They could explore the surface via telepresence far more thoroughly and rapidly than robots on the surface.

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

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

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

See my Will First Mars Astronauts Stay In Orbit - Tele-operating Sterile Rovers - To Protect Earth And Mars From Colliding Biospheres

Is This Why We Haven't Found Life On Mars Yet? Value Of Actually Looking


Skip to: Current classification of Mars as category IV

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

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

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

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

(Click to watch on YouTube)

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

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

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

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

(Click to watch on YouTube)

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

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

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


Skip to: It is practical to sterilize a modern rover

Currently the whole of Mars is classified as category IV

“…where there is a significant chance that contamination carried by a spacecraft could jeopardize future exploration.” We define “significant chance” as “the presence of niches (places where terrestrial microorganisms could proliferate) and the likelihood of transfer to those places.”

However it is then subdivided into categories IVa, b and c, where IVc is a region where terrestrial organisms are likely to propagate, or interpreted to have a high potential for existence of extant Martian life forms.

A Viking lander being prepared for dry heat sterilization – this remains the "Gold standard"[1] of present-day planetary protection. It was heated for 30 hours at 112 C.

A similar level of sterilization is currently needed for the “special regions”. The rest of Mars is considered to have conditions so harsh that only the pre-sterilization stage of Viking, cleaning the spacecraft with alcohol wipes in a spacecraft assembly clean room.

IVa is for regions of Mars like Gale Crater where Curiosity landed, where the local conditions are so harsh that they are thought to be equivalent in effect to the 30 hours of heat sterilization of Viking.

Curiosity was only required to be sterilized to the pre-sterilization levels of the Viking lander, with the Mars surface conditions doing the rest. IVb is for missions that search for life, where part or all of it might need to be sterilized even if it is not a special region (e.g. if it is going to drill down to life that can’t be contaminated from the surface).

For details see

It sounds as if the plan is to recategorize category IVa as II.


Skip to: How long to develop a 100% heat sterilized rover?

We have not yet sent any spacecraft to Mars sterilized to the levels of Viking. It is a challenge to do this, because modern spacecraft use components that are space hardened to withstand ionizing radiation but not usually able to withstand high temperatures. Though there are other methods approved and other development, dry heat remains an excellent way to sterilize a spacecraft, especially if the aim is to reach Viking standards or higher.

However this is not a limitation of modern technology as is sometimes assumed. We now have instruments and components that can withstand far higher temperatures than were possible at the time of Viking. We now have designs for Venus surface rovers that could potentially, with some work on further research, survive for a year or more at ambient temperatures on the Venus surface.

We have high temperature commercial components designed for deep oil wells, jet engines, cameras placed inside ovens, electric cars to save weight and so on. We have solar panels that could work at Venus surface ambient temperatures.

We could now design a rover for Mars that can be heat sterilized for months or even years on end at higher temperatures than for Viking. We could heat it up to 300 C during the journey out to Mars which would be enough not just to sterilize it, but to break apart DNA bases and amino acids.

Quoting again from my own survey of the research in my draft paper, then

Dry heat remains the “gold standard” of planetary protection (actually with a small amount of humidity to help decompose the organics, despite the name). To sterilize electronics we need to create conditions that electronics can tolerate but life can’t.

The other methods that are approved by NASA and ESA are gamma radiation, and low pressure hydrogen peroxide. There are many other ideas under investigation (Pugel et al, 2017).

The temperature of an oil well goes up by 25 °C for each kilometer of depth. Now that shallower oil fields are exhausted, oil is extracted from "hostile wells" with temperatures in excess of 200 °C and pressures in excess of 25,000 psi (over 1,700 atmospheres). Cooling is not practical in those conditions so they need electronics that can work at those temperatures.

High temperature electronics also save weight on planes. They don't have to be cooled, and they can be placed closer to the engines. This helps with cost, weight and most important, reliability (there are no worries about what happens if the cooling system fails). Electric cars also can be more reliable, weigh less and cost less if the electronics can be placed right next to the engine components at high temperatures. High-Temperature Electronics

High temperature mechanical components, sensors and cameras are all possible with the correct choice of components. The batteries and solar panels are best replaced by RTG’s (Radioisotope Thermal Generators) which can withstand high temperatures. Radio communication can be done with high temperature components and high temperature mechanical components are also possible. All these ideas have been explored in the Venus rover design studies.


The simplest way to do this might be to use the spacecraft to heat itself. If it uses an RTG as a source for power, it can also be used as a heat source too. Typically an RTG has an active cooling system or heat radiators. If this is disconnected, with the insulation of the vacuum of space, the RTG could heat the entire spacecraft during the journey out.

The lowest temperature of 200 °C would sterilize it of all life during a six months cruise.

This might still permit forwards contamination by RNA, proteins, etc. This could be significant, especially if it might explore prebiotic chemistry or early life. Also, GTAs could transfer properties of Earth microbes via lateral gene transfer to life related to modern DNA based Earth life.

However, at 250 °C the half life of the RNA bases under hydrolysis is between 1 and 35 minutes, with U the most stable, G and A of intermediate stability and C decomposing most rapidly. This suggests that if it is heated for several months at 250 °C, so long as some water vapour is available for hydrolysis of the bases, then there is not likely to be any genetic material remaining by the time it reaches Mars. If the temperature can be raised to 350 °C then the half-lives are between 2 and 15 seconds (Levy et al, 1998).

300 °C should be enough to destroy proteins too. Eight of the 20 amino acids, G, C, D, N, E, Q, R and H, have been proved to not just evaporate or liquefy but to decompose at temperatures between 185 for Q (Glutamine) to 280 for H (Histamine) For the other amino acids, they were not able to completely characterize the gases emitted. (Weiss et al, 2018)

There might be other more recalcitrant organics remaining but it seems that this should be sufficient to make sure no genetic material reaches the destination.

Are 100% sterile rovers and instruments possible in the forward direction?


Skip to: Back to the 2015 review

We can even develop a rover capable of traveling over the Venus surface, an automaton rover with limited electronics able to withstand 500 °C

The authors estimate a development time of 5–6 years and a cost of hundreds of millions of dollars.

Sauder, J., Hilgemann, E., Johnson, M., Parness, A., Hall, J., Kawata, J. and Stack, K., 2017. Automation Rover for Extreme Environments. - section 5.

They propose using their technology for contamination control:

We propose a novel approach that enables a long duration Venus rover mission by pairing clever, robust mechanisms with high temperature electronics that exist today. Electronic complexity is reduced by implementing mechanical analog systems in areas where electronics fall short. The final system is one in which the best of both high temperature electronics and mechanical systems are combined to make a system more capable than either technology on its own. Although the concept does not require significant advances in high temperature electronics, any developments in that area enhance the proposed concept.

An automaton rover could be subjected to much higher contamination control procedures than traditional rovers. It could be baked at extremely high temperatures, irradiated, and subjected to multiple chemical baths to kill any bacteria. Thus, automatons would be valuable in highly contamination control sensitive environments, like collecting samples from the dark, water streaks on Mars. In this type of situation, the automaton would likely be working in tandem with a traditional Mars rover


Skip to: What the new report says

The 2015 review proposed modifications to 15 of the findings in the 2014 report, didn’t support one of them[39]., and said that some important aspects were not covered in the 2014 report.[43]

I have a short summary of its findings in the section Mars special regions

in my extended version of the Wikipedia article: Planetary protection

I also have a longer summary in the separate article here:


Skip to: Would permit private space

Supporting Finding: Various scientific studies 4 , 5 , 6 , 7 suggest that the survival and amplification of terrestrial biota are unlikely on the Martian surface, which would support classification of much of the Martian surface as Category II.

Major Recommendation:

NASA should reconsider how much of the Martian surface and sub surface could be Category II versus IV by revisiting assumptions and performing new analysis of transport, survival and amplification in order to reassess the risk of survival and propagation of terrestrial biota on Mars. All past U.S. landed missions have been treated as though there is a “significant” chance that terrestrial organisms can survive and be transported to areas where life or biosignature detection experiments would be performed. Rummel et al. (2014) have shown that many areas of the surface are not locations of PP concern. Similarly, although there may be subsurface regions that continue to warrant additional special PP consideration, this need not be the case for all subsurface regions . NASA should revisit the categorization of areas that are not considered to be “Special Regions” and determine limits on terrestrial bioload transport and amplification from current landing sites.

I hope I have said enough here to suggest reservations with this suggestion that much or even any of the martian surface can be appropriately reclassified as category II.


Skip to: Not concerned about Elon Musk deliberately extinguishing Mars life

They also say that it is impractical to require launch providers or satellite hosts to ensure that their payloads for Mars are free of biological contamination. They say that instead of doing that there should be a system of sanctions - that private space missions are penalized for contaminating Mars.

What good is that?

They gave the example of the Beresheet lunar lander which had tardigrades onboard and this was not declared and they didn’t follow the planetary protection requirements for such missions.

There is no risk of forward contamination on the Moon, but there is a requirement to declare such things so that other missions can take account of them. If they find tardigrades on the Moon they know they came with this Israel lander.

This report suggests that nothing needs to be done to require launch providers to check that the spacecraft comply with the planetary protection requirements. I.e. it is supporting the status quo where a private mission sometimes doesn’t declare what it has on its spacecraft.

Here is the text of it:

Supporting Finding: It is impractical for launch providers or satellite hosts to definitively determine the biological content of every payload. Biological materials intentionally added by a bad actor are especially challenging for launch providers to monitor or report, as they can be further obscured by falsified verification or inaccurate documentation.The recent experience in which a launch customer placed tardigrades and other biological samples on the SpaceIL Beresheet lunar lander is illustrative. By the Moon’s Category II PP designation, it is likely that a payload license would have been readily granted had the bioload been self-reported; however, the lack of such reporting created new issues relating to launch licensing.

Supporting Recommendation: Breaches of PP reporting or other requirements should be handled via sanctions that hold the root perpetrator accountable, rather than increasing the verification and regulatory burden on all actors.

If this is applied to Mars, it would mean that e.g. Elon Musk could send a mission to Mars that has lichens in it, say, as an experiment to see if they survive on Mars, and if he doesn’t declare this, it might not be detected until after it has got to Mars and the life starts to grow on Mars (if it does).

In a situation like that it seems that he would just be penalized and there would be no requirement before the mission to check that he isn’t doing such a thing.

If applied to Europa, say, there would be no check made to make sure they are complying with the requirement to protect Europa's ocean from Earth life. That they would just be penalized if they did this.

This is perhaps even more significant than the recategorization of parts of Mars as category II, as it opens up the solar system to private space to send missions anywhere and there would be no check done on what they have in their payloads. How can we have a planetary protection policy in the forwards direction if it's only required to check the government missions for compliance?


Skip to: We don't need Mars as a backup

Elon Musk, though he is so in favour of sending humans to Mars as quickly as possible, does care about the science impact of introducing Earth microbes to Mars. Here he answers a question on this topic, in the 2015 AGU conference in San Francisco, 30 minutes into this video:

Q. "I am Jim Crawl from Arizona State University. I was listening to doctor Chris McKay, another advocate of humans to Mars, and he was talking about when we do go to Mars and if we find life either currrently there or extinct, we should consider removing human presence so that we can allow that other life to thrive. I was wondering what your thoughts on that were. "

A. "Well it really doesn't seem like there is any life on Mars, on the surface at least, we are not seeing any sign of that. If we do find some sign of it, then for sure we need to understand what it is and try to ensure that we don't extinguish it, that's important. But I think the reality is that there isn't any life on the surface of Mars. There may be microbial life deep underground, where it is shielded from radiation and the cold. So that's a possibility but in that case I think anything we do on the surface is really not going to have a big impact on the subterranean life.".

So, it's clear (as I'd expect actually), he does think it is important we don't extinguish any native Mars life. But he thinks there isn't any present day life on the surface.

The problem rather would be that he might make an executive decision that he doesn’t think there is any risk of making Martian life extinct, based on an imperfect understanding of the situation there. He might not pay attention to the ideas of astrobiologist or even know about them.

It would be too late if he later found out to his regret that he had made native martian life extinct.

Please NASA do reconsider this proposal and take account of more recent findings than that 2014 report. Thanks!

There is so much we can do by way of human exploration on the Moon first, and then to explore Mars from orbit.


Skip to: Billions of dollars commercial potential of extraterrestrial biology

Sometimes the colonization enthusiasts will say we need Mars as a backup for Earth in case something happens to Earth.

Well - let’s do a backup of seeds on the Moon. The darkest craters there have natural cryogenic conditions at the temperature of liquid nitrogen. It could expand to a small colony too. The point in it would be as for the seed vault in Svalbard in Norway - a very secure seed backup, where seeds remain viable through passive cooling centuries later, even unsupervised. That makes sense. We can have a small caretaker colony and a library.

It’s been suggested a few times, especially by William Burrows. I go into the idea here:

Usually the point in a backup is to restore after all.

The main thing that could happen to Earth and not to Mars would be an asteroid collision (though Mars is hit by far more asteroids than Earth).

However we have not been hit by anything large enough to sterilize Earth to the point that it is easier to survive on Mars than on Earth for billions of years. Probably never, given how harsh the conditions on Mars are.

For far less than the cost of an attempt to set up a Mars colony, we could send a few small infrared telescopes into space to complete the survey of Near Earth Asteroids quickly. We could also complete the Breakthrough Starshot array, which would give us the ability to deflect comets too, long period comets. Those rarely come anywhere near Earth, typically pass by further away than the sun, and the nearest any has come is Lexell’s comet in 1770 six times further away than the sun.

We would then be protected - surely it is better to protect Earth than to have a plan that would involve abandoning it - but not only that. It’s hard to think of any scenario that could end up with Earth more habitable than Mars.


Skip to: Robert Zubrin's argument that we have an obligation to establish ourselves on Mars

Even if you are not interested in science, there is also a huge commercial motive for preserving alien astrobiology if we find it on Mars. We already have a billion dollar industry based on enzymes from cold and from heat adapted extremophiles. There could be multiple billion dollar future industries based on alien biochemistries, which could be lost if we introduce Earth life in a way that makes the martian life extinct, which is the worst case scenario.

I have sections about this in my Touch Mars? book to read up more, Benefits to humanity from astrobiology.

New dimensions to biology

It's opening up a new field of discovery that would inspire young biologists and surely invigorate the entire field of biology in ways we can't predict. That by itself is an immediate benefit. This might lead to innovations in biology, medicine, nanotechnology, etc at a fundamental level. Though so hard to predict, these may be the most transformative.

New biological materials

We have many products of microbes such as

  • Food stuffs: cheese, butter, yoghurt, alcoholic drinks such as wine and beer, soy sauce, miso, protein (e.g. from spirulina),
  • Drugs such as antibiotics, steroids,
  • Materials such as polysaccharids used to thicken and stabilize food, as a base for cosmetics, to extend blood plasma
  • biofuels
  • vitamins, enzymes, amino acids,

Microbes from another planet might give us new products, or be able to generate the products more efficiently

Genetic firewall

It might be that some or all the martian life has no resistance to Earth life (e.g. early life), or that it can't survive in any of the habitats on Earth (e.g. it only survives in very cold conditions on Mars). If so, it could also be the ultimate in a genetic firewall.

We could use it to generate exotic chemicals with no risk at all that our microbes will escape into the wild and cause harm there, or hybridize with Earth life.

Enzymes from extremophiles

I'm going to summarize some of the examples given in a survey paper Cold and Hot Extremozymes: Industrial Relevance and Current Trends (paper from 2015) and this section is taken entirely from that paper, published in "Frontiers in Bioengineering and Biotechnology". I'll mention some of the highlights, They give many more examples and describe them in detail.

These enzymes are now used

  • in the food industry, including bread making, fruit juices, for lactose free foods, for making syrups
  • in the $1 billion industry of enzymes for detergents
  • for wood pulp and paper processing
  • in the textile, cement, cosmetic industries.
  • in various research techniques for experts studying DNA and RNA

They are used to reduce costs, make the processes more ecofriendly, reduce CO2 emissions, more efficient faster processing, etc et

Industrial applications of astrobiology already- enzymes from extremophiles

Cold adapted extremophile enzymes

These are more active, and active at lower temperatures. This means you need less of them to get a result, and you don't have to heat them up and they can work at low temperatures. As an example, this lets you reduce washing temperatures and to help people with limited access to warm water. The global market for detergent enzymes is valued at over $1 billion

They may also be inactivated as they get hotter, which is useful if you want to use them only for a particular length of time, e.g. meat tenderization.

Other applications include

  • Production of lactose free foodstuffs. The cold active enzymes let you do this at lower temperatures.
  • Fruit juice processing for clarification and to reduce viscosity, and extract natural oils.
  • Bread making. Let's dough prove at lower temperatures.
  • Textile, research, cement and cosmetic industries -as a low temperature antioxidant enzyme.


Heat adapted extremophile enzymes

These are active and efficient at high temperatures, extreme pH values, high concentrations of the substrate, and high pressures. They are also highly resistant to organic solvents, and other things that stop enzymes working (denaturing agents). They are easier to separate during purification steps (because they don't break up) and they catalyze faster reactions.

  • Enzymes from extremophiles are useful for production of glucose syrup from starches, for instance corn (maize).
  • They are also useful for "baking, brewing, the preparation of digestive aids, and in the production of cakes and fruit juices"
  • Also they are useful for the paper making industry. The first stage is to extract pulp from wood, fibre crops and waste paper. This is normally done using extremely high temperatures of over 60 °C, alkaline pH and strong chemicals like sodium sulfide, sodium hydroxide and chlorine.

    They are also useful for bleaching the paper to make it white, to remove sticky patches of pitch, to make the paper brighter and stronger and increase the overall efficiency.


We can’t even begin to guess how many applications of a totally alien biochemistry there would be.

If life on Mars has evolved for billions of years it’s likely not just one species of microbe or a few species. There’s no reason why there can’t be thousands, or millions of different species, with different capabilities.

This next section of this article is from my draft paper:


Skip to: We are our biosphere's intelligence to avoid catastrophes

Robert Zubrin has an argument which he presented in the "Making of" episode 0 of season 1 of the National Geographic series Mars (Zubrin, 2016).

"I would say that we have not only the right, but the obligation, to go and establish ourselves on Mars. We are the creatures with all of our flaws that the Earth's biosphere has evolved to allow itself to reach out and establish itself on additional worlds. And we will take this nearly dead world and we will create a fully living world there. And so there'll be new species of birds and fish and plants. And it will be magnificent. No-one will be able to look on it and not feel prouder to be human."

We provide a way of getting into space, yes. But if Earth evolved us to reach out and establish itself on other world,s, it also evolved us with the intelligence, foresight, and deep scientific and ethical understanding to guide that exploration. We are the Earth's biosphere's guiding intelligences in space, and that may be one of our main roles.

For instance one of the main reasons for going into space may be to protect Earth from hazards (such as asteroids), or to find resources for use on Earth, or to increase our understanding of ourselves, and of science, biology and the universe, or indeed, as a place for adventure and recreation. We have already found many benefits for Earth’s biosphere, already, through our satellites in Earth orbit.

It's not automatic that what anything humans find inspiring and want to do is going to work, and is going to be harmless to ourselves or to others. For instance deliberate introduction of the European wild rabbit into Australia for sport led to many problems (Fenner, 2010).

Also, the solar system is vast with many other places of great interest where we can visit, and even set up home, without risk of contaminating them.

Yes, we can set up those magnificent habitats that Robert Zubrin talks about in settlements constructed from materials in the asteroid belt. There is enough by way of materials there to create habitats with total living area equal to that of a thousand times the land area of Earth. We can also set them up on Callisto, and in the lunar caves, which may be over 100 kilometers long and up to 5 kilometers in diameter in the low lunar gravity.

We could paraterraform Titan if there is no native life there to be made extinct, more easily than anywhere. It has abundant wind and hydro power which could power electric lighting for agriculture in vast habitats that straddle the entire moon.

So, yes, we could set up habitats in space and indeed they could be magnificent. But there is no urgent need to go to Mars right away to do this. There are many other places to try it, and given the special planetary protection issues for Mars, we can take the time to study Mars first and decide what to do based on what we find there.

Earth using us to reach into space and “it will be magnificent” - Robert Zubrin


Skip to: Let's go into space in a way that respects science and values extraterrestrial life

We are our biosphere’s way of getting into space and visiting other planets as Zubrin suggests. But we are also its noosphere (de Chardin 1932), its intelligence that it can use to avoid potentially catastrophic consequences. We already have used this, for instance to prevent extinction of blue whales, and to feed billions through the green revolution. We are working together to rise to the challenges of climate change and biodiversity loss.

By acting as a thinking biosphere, we can also plan our missions in space in such a way as to keep our options open. We can advance into space as humans and robots together, each doing what we do best, with the robots as our eyes, and hands, in regions we cannot yet explore in person. Just as we can't send humans to the surface of Venus for some time yet, because of the extreme conditions there, there may be other regions we need to keep away from for now because of the uncertain effects, in both directions, from collisions of biospheres.

If it is true that other biospheres are as potentially vulnerable as this article suggests, perhaps this is a time to start a serious development program with the aim of 100% sterile landers and rovers for astrobiological exploration. This would be a joint program with the Venus rover project.

Although this would take some time and would involve some expense, the pay off would be huge. With 100% sterile rovers we could then send our robotic astrobiological explorers anywhere in our solar system, including the depths of Enceladus and Europa, without any more concerns about forward contamination. We can then decide what to do next based on knowing what is there, and what is at risk.

We are our biosphere’s noosphere - its thinking component


Return to top

We can go into space also for space mining, and for discovery, for tourism, for many reasons. But let’s also do it in a way that respects science.

As Arthur C. Clarke put it eloquently in that story:

This world around them was no longer the same; Venus was no longer dead – it had joined Earth and Mars. For life called to life, across the gulfs of space. Everything that grew or moved upon the face of any planet was a portent, a promise that Man was not alone in this universe of blazing suns and swirling nebulae. If as yet he had found no companions with whom he could speak, that was only to be expected, for the lightyears and the ages still stretched before him, waiting to be explored. Meanwhile, he must guard and cherish the life he found, whether it be upon Earth or Mars or Venus.

We would now say whether it be upon Mars, Europa, Enceladus, Ceres, and just possibly the upper atmosphere of Venus as well as other places we may not have discovered yet.

In the long term we have an exciting future ahead of us. We may send humans to Callisto, which is resource rich, covered in ice, protected from ionizing radiation by the Jovian magnetic field and yet well away from its own ionization belts.

Perhaps we may send them to Titan where they would not need pressurized spacesuits, but low tech gear not far off diving gear from an outdoor sports shop, and heaters for feet and hands.

We might eventually convert all the material in the asteroid belt into habitats - there are enough materials there for radiation shielding for habitats with a total area a thousand times the land area of Earth.

There are many possibilities in the far future. However we leave a far more interesting, varied solar system to our descendants if we guard and cherish the native life we find, as we explore.

Long term we may be spreading out into the galaxy. Even the entire galaxy may not be enough for non sustainable exponential growth over hundreds of thousands of years, or millions of years.

If we learn to protect and cherish our “pale blue dot” and we develop circular economies, and sustainable living in the solar system, and practice planetary protection in our own solar system, this is good preparation for eventual responsible and sustainable exploration of the galaxy beyond.

This is the topic of the essay I wrote as my submission for the 2019 “Nine dots prize”:

See also my

Read online for free here: OK to Touch? Mars? Europa? Enceladus? Or a Tale of Missteps?

Or buy here Touch Mars? Europa? Enceladus? Or a Tale of Missteps - Amazon.com

Read online for free here: Case For Moon First:

Or buy here: Case For Moon First: - Amazon.com

Read online for free here: Why Humans on Mars Right Now are Bad for Science. Includes: Astronaut gardener on the Moon

Or buy here: Why Humans on Mars Right Now Are Bad for Science- Amazon.com

And here is my astrobiology article that I’m working on - it may have some points of interest. It is not peer reviewed - this is an early stage, where I’m sharing it for comments and reactions but hope to submit parts of it for publication at some point.

Potential Severe Effects of a Biosphere Collision and Planetary Protection Implications

See also the essay I did as a submission for the nine dots prize:

Our pale blue dot - any other home for us in our universe?