Certain strains of bacteria, including Bacilus Pumilus, may be able to survive on the Martian surface. Image credit: NASA

Bacteria Could Survive in Martian Soil

Article Updated: 24 Dec , 2015

Multiple missions have been sent to Mars with the hopes of testing the surface of the planet for life – or the conditions that could create life – on the Red Planet. The question of whether life in the form of bacteria (or something even more exotic!) exists on Mars is hotly debated, and still requires a resolute yes or no. Experiments done right here on Earth that simulate the conditions on Mars and their effects on terrestrial bacteria show that it is entirely possible for certain strains of bacteria to weather the harsh environment of Mars.

A team led by Giuseppe Galletta of the Department of Astronomy at the University of Padova simulated the conditions present on Mars, and then introduced several strains of bacteria into the simulator to record their survival rate. The simulator – named LISA (Laboratorio Italiano Simulazione Ambienti) – reproduced surface conditions on Mars, with temperatures ranging from +23 to -80 degrees Celsius (73 to -112 Fahrenheit), a 95% CO2 atmosphere at low pressures of 6 to 9 millibars, and very strong ultraviolet radiation. The results – some of the strains of bacteria were shown to survive up to 28 hours under these conditions, an amazing feat given that there is nowhere on the surface of the Earth where the temperatures get this low or the ultraviolet radiation is as strong as on Mars.

Two of the strains of bacteria tested – Bacillus pumilus and Bacillus Nealsonii – are both commonly used in laboratory tests of extreme environmental factors and their effects on bacteria because of their ability to produce endospores when stressed. Endospores are internal structures of the bacteria that encapsulate the DNA and part of the cytoplasm in a thick wall, to prevent the DNA from being damaged.

Galletta’s team found that the vegetative cells of the bacteria died after only a few minutes, due to the low water content and high UV radiation. The endospores, however, were able to survive between 4 and 28 hours, even when exposed directly to the UV light. The researchers simulated the dusty surface of Mars by blowing volcanic ash or dust of red iron oxide on the samples. When covered with the dust, the samples showed an even higher percentage of survival, meaning that it’s possible for a hardy bacterial strain to survive underneath the surface of the soil for very long periods of time. The deeper underneath the soil an organism is, the more hospitable the conditions become; water content increases, and the UV radiation is absorbed from the soil above.

Given these findings, and all of the rich data that came in last year from the Phoenix lander – especially the discovery of perchlorates –  continuing the search for life on Mars still seems a plausible endeavor.

Though this surely isn’t a confirmation of life on Mars, it shows that even life that isn’t adapted to the conditions of the planet could potentially hold out against the extreme nature of the environment there, and bodes well for the possibility of Martian bacterial life forms. The LISA simulations also indicate the importance of avoiding cross-contamination of bacteria from Earth to Mars on any scientific missions that travel to the planet. In other words, when we finally are able to definitively test for life on our neighboring planet, we don’t want to find out that our Earth bacteria have killed off all the native lifeforms!

Sources: Arxiv papers here and here.


22 Responses

  1. Manu says:

    I foresee a strong objection to manned missions to Mars, here.
    It’s quite difficult already to avoid contamination by one probe. It will probably be just impossible to avoid when there’s actually a bunch of people up there.

  2. Dave Finton says:

    Manu: That would be an interesting debate. History is rife with examples of how “alien” species can out-compete local ecosystems right here on Earth, with often-times disastrous consequences.

  3. TD says:

    @Manu – This argument doesn’t make sense. If we find life on Mars, there will be renewed interest in going there. Billions will be poured into the space effort.

    I think the “be afraid to go there” argument is meant to scare the space industry into NOT finding life on Mars. The opposite is actually true. If we don’t discover and analyze life on Mars, then the next meteor from there (carrying a microbe) could spell doom for the human race anyway. We fund a spacewatch program to look for dangerous earth-crossing asteroids. We don’t ignore the threat..we spend money to study it. If we’re meant to be a species that has a place in the galaxy, I’d rather do it with my head held high, looking forward. It’s time to address these questions as one human family, not cowering in some dark lab avoiding them. Find life on Mars, study it safely, and be honest with the society that pays the bills.

  4. Torbjorn Larsson OM says:

    Biologically, populations that haven’t adapted to the environment, and that includes other species by coevolution, wouldn’t be expected to have a chance against the indigenous life.

    Those “alien” species are a great example, they out-compete local ecologies by being adapted to similar conditions while being freed of existing competition and parasitism. They find the same niches, except that they are larger.

    No such luck for terrestrial life on other planets.

    it shows that even life that isn’t adapted to the conditions of the planet could potentially hold out against the extreme nature of the environment there,

    Endospores that can’t metabolize nor reproduce, and have to be teased back to life afterwards at an observable ratio (in the paper 10^-5 survivability), are rather worthless as indicators of habitability IMHO. They are incredibly tough critters, which are produced solely for dormancy.

    Survivability isn’t habitability.

    That said, the experiment is interesting. Next step would be to establish subsurface habitable conditions (i.e. actually reproducing populations). How deep is any existing Mars life?

  5. Manu says:

    @ TD:

    I’m starting to see a pattern in some recent debates here about human exploration: critics are dismissed with either “irrational fears” (quoted from another post), “be afraid to go there” and “cowering in some dark lab”.

    Ridiculing your contradictor is a last resort when you run out of valid argument, I believe. My comments may be blunt at times, but I don’t think I have ever posted that sort of dismissive stuff.

    Taking part in the debates here is my humble way to “address these questions as [part of the] human family”. There’s not much of a point in debating without a diversity of opinions.

    Besides, please note my post implies a simple question: how to avoid contamination when there will be people up there. I’d be happy to read your ideas on this technical point. Meanwhile, please spare me the likes of “…my head held high, looking forward”. I’m sorry, I want nothing to do with that kind of sinister rhetoric.

    @ Torbjorn:

    Thanks for your civil and argumentative answer. You certainly have a point there.

    However, it’s this kind of consideration which led Jpl (or was it Nasa?) to crash Galileo into Jupiter instead of Europe.

    I agree Earth organisms wouldn’t have much chance of competing right away against a Martian ecosystem; but I don’t think we can honestly say this chance is exactly zero, esp since we don’t have much idea what Martian life could be. Besides, Martian life if any, is probably scarce and not near the surface. Earth organisms might have a good deal of time to adapt to local conditions before meeting any ‘alien’.

  6. Torbjorn Larsson OM says:

    Here is a podcast about Mars subsurface analogous biospheres, namely caves, by Carl Zimmer and Hazel Barton.

    Notably in this context is first and foremost a segment ~ 20 minutes in, when they discuss biological contamination. What happens in caves is that life is so harsh (poisonous minerals), starved (no photosynthesis) and competitive (lots of oddball antibiotics) that surface bacterias die out, unless they are constantly replenished by human visitors.

    They also discuss previous to that how varied the bacterial communities are, typically ~ 1 k species. The reason seems to be that they need to do services for each other, no single bacteria can supply all of the required metabolism. [The “community” found in a South Africa deep mine of a single bacterial species loaded with archaebacteria genes and other stuff it has picked up by gene transfer is an exception that comes to mind. But that bacteria lives in the rock, on fairly energy rich hydrogen released by radioactive minerals, not in a cave.]

    Also, these ecologies are old. They can trace relatedness all over the world, and one parsimonious reason may be that these communities have split and moved by plate tectonics!

    @ Manu:

    Thank you!

    I agree that the probability for contamination can never be zero. OTOH science have to use a reasonable cutoff in all matters, a 3 sigma guarantee, say by using cave communities as models, would be a reasonable safe guard. Likely Barton already sits on the necessary material, as she points out that there is no contamination problem for her, as long as she avoids frequently visited cave volumes.

    I’m sorry, but I don’t see how Earth bacteria will be able to adapt to conditions that any indigenous life hasn’t already mastered. If we would 1) drag these cave or rock community bacterias, 2) in full, with us to Mars and then 3) specifically implanted them deep down, I would give them a small chance of competing in niches that may be similar enough to what they can survive in – but we will do none of these three things.

  7. TD says:

    @Manu – I’m sorry if I sounded disrespectful. And I meant nothing sinister by approaching the question of life on Mars as “one human family”, “head held high”….quit the opposite. But I am trying to get a handle on who is saying we shouldn’t go to Mars if there is life there. Who is? I am constantly hearing people say “we better be careful, because if we find life on Mars some people will argue we shouldn’t go there”…but they refer to other people making that argument, not themselves. Do you think we shouldn’t go to Mars if there is life there?

    Just to give my opinion, I think we’d be crazy, and risk humanity, not to. Like I said, the next meteor from Mars could contain the deadly microbe anyway. Whether it falls in Canada or the ocean – we’ll have much less chance to find and contain it, than if we go right to the source – Mars. It will cost billions and risk lives, but that is what exploration is all about.

  8. Aqua says:

    I’m thinking transpermatic endospores are mutagenic and will survive wherever and whatever level of preconditioned environmental elements are in place and/or will rapidly mutate to the level of survival. Mutants rule?

  9. Aqua says:

    Can you say Trick or Treat you little extremophiles?

  10. Pvt.Pantzov says:

    seed mars.

  11. Aqua says:

    OR, perhaps as they say in L.A. – Seed THIS!

    I.E. Put yer pants back on…. there are dangerous cactus out there!

  12. Lawrence B. Crowell says:

    Invasive species usually proliferate in a new environment because there are no predictors or, in the case of plants plant eaters, to keep the numbers in check. Kudzu in the south is an example. Most Earth bacteria would have a hard time on Mars I would suspect. and just as a tropical plant is not likely to be invasive in Alaska, the same might hold here. Of course this involves words like “might,” and is conjectural.

    The 1976 Viking experiments found chemical responses corresponding to life, but it was dismissed. Curiously the gases released had diurnal behavior, which makes it possibly biological. Possibly NASA might have backpedalled on this too quickly.


  13. Jon Hanford says:

    I thought everyone knew about how easy it is to terraform Mars, per the movie “Total Recall”. I thought this movie was based on actual events, not some totally unrealistic assumptions (like the current governor of California). 🙂

  14. Lawrence B. Crowell says:

    Terraforming Mars: Yep it was an idea I cam up with in grade school. I saw this movie called “Silent Running,” which was an improbable scenario of the last ecosystems from Earth in these large domes attached to a spacecraft. For some reason it was out around Saturn. The movie is largely about one guy on the spacecraft going a bit bonkers. Yet it occurred to me, “Why not land these domes on Mars, and set up biozones and eventually change the planet?” I had all sorts of drawings and idea about this.

    It is a nice dream in a way. It is also in keeping with aspects of the human imagination, where a person sees a prestine canyon and in their mind’s eye sees the construction of a dam there. These images from Mars are in many ways rather stunning in their own beauty. Maybe Mars is in a sense meant to be Mars and not remade into something like Earth.


  15. lomitus says:

    Bio domes vs. Terra forming…I think that it’s important to distinguish a difference here. While it would certainly be expensive by today’s standards, I think it has been safely proven that bio domes would certainly be possible on Mars. Certain precautions would have to be observed in regards to “Mars Quakes”, the high winds and harsh enviroment, etc., but in the end if we ever wish to put humans on Mars, that is essentially what we will need to do.

    Terra forming on the other hand is a -very- different idea completely. You can’t just go out and start planting trees and various types of vegetation on the surface of Mars (or any other planet we currently know of) in hopes of making it more “Earth like”…it just doesn’t work that way. Please let’s make sure we are aware of the differences between movies and fiction and the reality of the situation.

    Now in regards to the whole microbe and the “should we or shouldn’t we” debate, it should be clear to most intelligent people that more research is certainly needed. While certainly it will “cost millions and risk lives”, I would also point out…have we learned -nothing- from history? Should we -really- repeat the same mistakes that early explorers on this planet made? In a very small nut shell, should we “Boldly go” or should we study things and learn all we can -first-? Barring monetary issues, we have the ability to study this planet and to really think about and consider what we’re doing here. I’m NOT saying that we shouldn’t go…I’m saying let’s take our time and be -smart- about it and learn all we possibly can before we do go.

    -If- there is any kind of life on Mars, be it microbial or otherwise, we do NOT know what kind of threat…or benefit…this may have to human kind. To simply try and impose ourselves on it would be rash and very foolish. Human civilization as a whole is still a rather pathetic and disgusting thing with very little “respect for life” even here on our own planet. We still slaughter people by the thousands and tens of thousands over petty disputes in regards to garbage like politics and religion and we seem to think that everything within our grasp is somehow automatically “ours to do with as we please”. Do we really wish to carry these deplorable aspects of our culture with us as we venture out in to space?

    Let’s put this another way…how many beneficial things may be been wiped out completely by deforestation of the rain forests…things we didn’t even know about? Could we even have already destroyed a cure for cancer or other diseases? Now let’s apply this thinking to bacteria and microbial life on Mars…do we -really- want to destroy these things by just bungling in like fools?

    Sooner or later human kind -will- need to get past it’s short comings and we -will- need to move out to the stars. That said, we should do these things carefully and with a great deal of respect for where we are going so that it doesn’t come back and bite us in the arse as it has so many times in the past.

  16. Mr. Man says:

    I think that if there is any life on Mars, we should quarentine some of it into its own little reservation-like domes. Then we can go there without any fear of destroying them for good (cause there will always be some left in the reservation).

    Still, I don’t think that fear of harming life there should keep us from going, there are always risks…as its been mentioned before, if we focus too much on the risks involved in anything, nothing will ever get done. Sometimes you just have to do (you should still be cautious just not overly cautious). All I’m saying is its human to be a little daredevil, and we shouldn’t shun what makes us human.

  17. BeckyWS says:

    I think Manu and TD are talking at cross-purposes. There are 3 arguments about whether sending people to Mars is a good idea in relation to the life that might be there already:
    1) Possible risk to humans by pathological effects from Martian life- seems to be what TD is talking of.
    2) Increased risk of contamination with Earth-bacteria by sending people as they are harder to sterilise than rovers, thereby making false positive identification of Martian life more likely
    3) The possibility that Earth-based bacteria will wipe out indigenous Martian life, which seems to be what Lawrence and others are talking of.

    Personally I think there is an extremely strong argument akin to the First Directive of Star Trek, not to cause harm to indigenous life. OTOH, Mars is a big place, and whatever life is there is probably going to be very low-level bacteria-like, and therefore some human impact in small areas at least initially could be acceptable.

    Talking of caves, I have to wonder seeing the size of some of the collapsed lava-tubes, if these might not be prime sites for more complex life to develop. What is the likelihood of having liquid water in these features, some of which seem pretty deep, for example? I think they would be a great spot for future probes, if we can get energy indpendent of solar.

  18. TD says:

    Interesting comments. In summary, no one is saying avoid going to Mars completely, just be extremely careful if we do. Which means being open with society about the existence of life there, to attract the best and brightest to the tasks of avoiding forward contamination and avoiding reverse contamination. Any lesser effort is criminal negligence. Agreed?

  19. Lawrence B. Crowell says:

    BeckyWS comes pretty close to my thinking on this. In some ways this is a bit like treating the other planets as “parks,” in the same way national parks preserve, or are supposed to preserve, a region. This is particularly the case with a planet such as Mars, which could bear life and which we stand some chance of putting boots on the ground there. We need to ensure that our activities do not damage the natural systems there.


  20. Astrofiend says:

    Meh – the chance of Earth-based bacteria thriving and out-competing with indigenous bacteria – pretty much nil. That would be akin to an Emperor Penguin out-competing a desert scorpion – not adapted to that environment at all, and therefor almost useless in it. Same with the idea of martian bacteria being pathogenic to humans or other Earth-bound creatures – why would a bacteria that has evolved in isolation for potentially hundreds of millions of years in a freezing, high CO2, high radiation, extremely salty etc etc environment suddenly just happen to be able to infiltrate the human body, use our cells for their own sinister purposes and give us horrible new forms of hemorrhagic fever or something? Why would that all of a sudden be a good environment for their survival? We have these blinders on that make us think that Earth is optimal for life in every way, and if only poor little bacteria hunkering down and defying the harsh conditions elsewhere could just make it here, well they’d just love it and thrive like they never have before, like Earth is some sort of promised land.

    I think the only valid argument is that of potentially contaminating experiments designed to look for life on Mars. If we aren’t absolutely fastidious about preventing that, then we can’t just simply run the experiment again (easily) – we’ve stuffed it. But that’s it.

    Even if Earth-based bacteria did get a foothold (impossible in my opinion) – so what? Though some may disagree, Earth-based life is not some sort of dirty stain on the universe that must be contained. If we take some bacteria there and it competes successfully – good on it. Evolution will triumph again. There are conceivable ways that Earth based bacteria could have hitched a ride to Mars anyway by now, so does it make any difference if we’re the ones to bring it in? Like just because we are self-aware, that makes it somehow morally objectionable to do, like Adam and Eve and original sin? If we are to argue that we have some sort of self-imposed moral obligation to not disturb these lowest life forms, then lets just give up the whole idea of human exploration, because a human being is a veritable bag of bacteria and foreign contaminants.

  21. Richard Kirk says:

    We get a bunch of extremophile bacteria, and stick them in simulated Martian conditions. A day and a bit later, they are dead. When you consider the trouble we have in sterilizing hospital kit, this is pretty effective.

    I think we ought to avoid the risk of shipping life forms out to Mars: it would be a shame to discover some life form out there and not know whether it was a relative of something we had bought there earlier. However, if we happen to leave a fingerprint on a Mars lander, it would probably get sterilized anyhow. In fact, sterilizing the craft might kill off our regular bacteria and select the extremophiles that just might survive. You can’t win.

    The problem for Martian settlers might well be something non-living. We know Moon-dust is abrasive and clinging in a way earthly dust isn’t, and it smells of gunpowder, which suggests some funny chemistry. There well may be something chemical out there that we don’t normally meet on earth – perhaps because our life ate it long ago. It probably won’t be a ‘new’ chemical – just something a bit unexpected or out of place.

    A better title might have been ‘Bacteria Could Not Survive In Martian Soil’. Bot on-one would have read that, I guess…

  22. Lawrence B. Crowell says:

    The problem from a scientific perspective is that if Earth life is dragged to Mars it will contaminate any signal for the presence of martian life. This is one problem with sending astronauts to Mars. Given they would search for life and try to find signatures of life, they would have trouble with biological noise they drag with them. This would also be the case if tests are performed to find chemical signatures for precursors of life. It might be that life never got going on Mars, but that the chemical precursors for life existed, which are now in some “fossilized form.”


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