Ancient bacteria from Mars may be dormant in the deep layers

Science Book, October 25 (EFE). Ancient Mars bacteria could live near the planet’s surface for much longer than previously thought, and if they were also buried and protected from cosmic and solar radiation, they could survive even long.

The discovery – published today in the journal Astrobiology – raises the possibility that if there was life on Mars, its biological remains could be recovered by the ExoMars (ESA) and Mars Life Explorer (NASA) missions, sent back to Earth for their study. and pollute our planet.

But the implications of the research go further: If bacterial strains are able to survive in an environment as harsh as that of Mars, future astronauts and space tourists could also contaminate the Red Planet with their bacteria.

The article, led by Northwestern University (US) and whose details were published today in the journal Astrobiology, warns that terrestrial pollution on Mars could persist for thousands of years.

Conditions on Mars are harsh: the planet is very dry and cold (it averages -63°C at mid-latitudes), and it is constantly bombarded by intense cosmic and solar radiation.

To test whether life could survive in these conditions, the researchers determined the survival limits of microbial life for radiation and then subjected six species of terrestrial bacteria and fungi to similar conditions.

Thus, they note that some terrestrial microorganisms can live on Mars for geological time scales of hundreds of millions of years.

Researchers have found that the powerful microbe, Deinococcus radiodurans (nicknamed “Conan the Bacteria”), is uniquely suited to survive the harsh conditions on Mars.

In experiments, Konan survived massive amounts of radiation in a cold, barren environment.

In previous studies, researchers found that Konan’s bacteria, when suspended in a liquid, could survive 25,000 radiation units (or “grays”), the equivalent of about 1.2 million years below the surface of Mars.

The new study found that when the bacteria dries up, freezes and burrows deep – which would be typical of a Martian environment – it can withstand 140,000 grays of radiation, a dose 28,000 times higher than that which would kill a human.

Thus, although Konan could only survive for a few hours on the UV-exposed surface, he was able to survive much longer in the shade or under the surface of Mars.

The study indicates that Konan, buried 10 centimeters below the surface of Mars, the survival period of bacteria increases to 1.5 million years, and buried at a depth of 10 meters, can live 280 million years.

The researchers concluded that this means that if a microbe similar to Conan’s bacteria evolved during the period of the last water flow on Mars, its living remains could remain dormant deep underground. EFE

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