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Bacteria Could Survive in Martian Soil

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

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.

Comments on this entry are closed.

  • Richard Kirk November 1, 2009, 3:06 AM

    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…

  • Lawrence B. Crowell November 1, 2009, 10:54 AM

    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.”