Life on Mars? It’s possible. By simulating the hostile conditions of the Red Planet, a team of scientists has shown that bacteria and other single-celled organisms can survive the intense radiation to which Earth’s “cousin” is exposed for hundreds of millions of years.
Colonies of ancestral microorganisms could have survived on Mars for up to 280 million years and their traces could still be present in the subsoil. This is, in principle, the demonstration that comes from a new series of experiments, the results of which have appeared in the journal “Astrobiology”. The tests were conducted by Brian Hoffman’s group of Northwestern University in Illinois.
The researchers have reproduced the current conditions of Mars – frost and absence of water – and estimated that dehydrated and “hibernated” bacteria and yeasts can remain alive for up to a record duration of 280 million years: this threshold would consequently increase , the possibilities of finding traces of it, if the Red Planet really hosted life in the distant past.
Compared to previous attempts to demonstrate the plausibility of life on Mars experimentally, Hoffman and his colleagues took a novel approach: they dehydrated and frozen several species of bacteria and yeast before subjecting them to radiation similar to that which any underground life form would undergo. of Mars. They then measured the damage these dry, “asleep” microorganisms suffered.
“When you eliminate the water and cool the whole environment, the resistance of a living organism multiplies phenomenally,” explains Hoffman. It is a process similar to that of freeze-drying food to lengthen its preservation times. Mars is dry and cold and, therefore, it is likely that bacteria or other microscopic life forms under its surface have become too.
The samples of treated microorganisms were “touched” very little by radiation, surprising the researchers. “We have observed that dried and frozen cells of the D. radiodurans bacterium can survive astonishing amounts of ionizing radiation – exposures equivalent to a period of hundreds of millions of years.”
This extraordinary longevity could facilitate the search for evidence of life on Mars, particularly in samples that will return to Earth with missions such as NASA’s “Mars Sample Return”. Expected for 2027, it is the ambitious project to recover and study what was taken by the “Perseverance” rover, currently engaged inside the Jezero crater.
In other words, macromolecules such as DNA and proteins would remain intact much longer than the bacteria themselves and, however, there is also the risk that, if we had contaminated the planet, this contamination would be almost permanent. “If this contamination had happened, how do we know if what we find was there before we arrived or if it was deposited by us? – asks Hoffman -. If we cannot discern between what is terrestrial and what is truly Martian, so to speak, then it will be impossible to establish with certainty whether there is or was life.”
