Scientists have found that microorganisms can survive in the harsh surface conditions of Mars for millions of years, which is much longer than previously thought.
Do we have better chances of detecting life on Mars? [Image by NASA]
Mars isn’t the friendliest planet to life forms, single- or multi-cellular. We’ve long known that it would be somewhat difficult for life as we know it to last long on our red neighbor. The planet’s temperatures can reach as high as 35 degrees Celsius in the summer and as low as -143 degrees Celsius in the winter. The atmospheric pressure is about 0.05% of Earth’s, but that’s not the worst thing yet. There’s also quite a lot of radiation, which can affect the type of life that can thrive on the surface.
Thus, all of this begs the question: can life survive on Mars under those conditions? And if there is life on Mars, how long can it survive? A new study sought to answer these questions, coming to conclusions and findings that can inform the search for life elsewhere in the universe.
Mars's thin atmosphere and red surface [Image by NASA/Viking 1]
Scientists wanted to know the limitations of microorganisms when it comes to surviving extreme conditions. If scientists can determine these limits, they can identify biomarkers and assess the chances of survival of microorganisms elsewhere in the galaxy. This can then aid mission planning as well as the further development of techniques in the search for extraterrestrial life.
A team of researchers from the Lomonosov Moscow State University wanted to see how much radiation microorganisms can endure in Arctic permafrost sedimentary rocks, in low temperature and pressure. Sedimentary rocks are considered to be the Earth equivalent of regolith, a term that refers to surfaces weathered by space. The researchers assumed that radiation damage is the factor that’s most likely to limit the lifespan of these microorganisms.
Simulating conditions on Mars entailed the use of an original constant climate chamber. The researchers then subjected the microorganisms to different levels of gamma radiation. The results of the experiment showed that the microorganisms had a high resistance to the low pressure and temperature in the simulated Martian environment.
However, the radiation seemed to have had an effect on the microorganisms in the constant climate chamber. The study was able to do something that other studies haven’t been able to do in the past: keep prokaryotes alive in radiation levels beyond 80 kGy.
Arthrobacter bacteria [Image by T. Tamura, T. Nishii & K. Hatano]
“It is also important that in this paper, we studied the effect of high doses (100 kGy) of gamma radiation on prokaryotes’ vitality, while in previous studies no living prokaryotes were ever found after doses higher than 80 kGy,” said Vladimir S. Cheptsov, one of the researchers.
Cheptsov and his colleagues found that the number of prokaryotic and metabolically active bacterial cells that they started the study with remained the same. However, there was a change in the dominant types of bacteria in the chamber. The population of a type of bacteria called Arthrobacter was found to have increased in the chamber. This indicated that Arthrobacter bacteria can thrive in the conditions on Mars.
According to Cheptsov, it’s possible for this type of bacteria to survive “in anabiotic state in the surface layer of regolith (protected from UV rays) for at least 1.3-2 million years, at a depth of two meters for no less than 3.3 million years, and at a depth of five meters for at least 20 million years”. That’s a nice long time to live, and it increases the possibility that we may find extraterrestrial albeit microscopic forms of life on Mars.
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