Bacteria Could Survive in Martian Soil
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.
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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.
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.
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?
Can you say Trick or Treat you little extremophiles?
seed mars.
OR, perhaps as they say in L.A. – Seed THIS!
I.E. Put yer pants back on…. there are dangerous cactus out there!
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.
LC
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).
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?
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.
LC