Ancient Mars may have had an environment capable of harboring an underworld teeming with microscopic organisms, French scientists reported on Monday. But if they existed, these simple lifeforms would have altered the atmosphere so profoundly that they would have triggered a Martian ice age and become extinct, the researchers concluded.
The results provide a grim view of the ways of the cosmos. Life – even simple life like microbes – “could actually often cause its own death,” said the study’s lead author, Boris Sauterey, now a post-doctoral researcher at Sorbonne University.
The results “are a bit grim, but I think they’re also very uplifting,” he said in an email. “They challenge us to rethink how a biosphere and its planet interact.”
In a study published in the journal Nature Astronomy, Sauterey and his team said they used climate and terrain models to assess the habitability of the Martian crust 4 billion years ago, when the Red Planet was thought to be level with the water and much more hospitable than today.
They speculated that hydrogen-guzzling, methane-producing microbes would have thrived just below the surface at the time, with several inches (tens of centimeters) of dirt more than enough to shield them from harsh incoming radiation. According to Sauterey, any ice-free place on Mars could have swarmed with these organisms, just as they did on early Earth.
However, the hot, humid climate of early March would have been compromised by so much hydrogen being sucked out of the thin, carbon dioxide-rich atmosphere, Sauterey said. As temperatures plunged nearly -400F (-200C), any organism at or near the surface would likely have gone further in an attempt to survive.
In contrast, microbes on Earth may have helped maintain temperate conditions, given the nitrogen-dominated atmosphere, the researchers said.
Kaveh Pahlevan of the SETI Institute said future models of Mars’ climate should take French research into account.
Pahlevan conducted a separate recent study suggesting that Mars was born wet with warm oceans for millions of years. The atmosphere would have been dense and mostly hydrogen at the time, serving as a heat-trapping greenhouse gas that was eventually transported to higher altitudes and lost to space, his team concluded.
The French study investigated the climatic effects of possible microbes when Mars’ atmosphere was dominated by carbon dioxide and is therefore not applicable to ancient times, Pahlevan said.
“What their study clearly shows, however, is that if (this) life were present on Mars” during this earlier period, “they would have had a major influence on the prevailing climate,” he added. in an email.
The best places to look for traces of this past life? French researchers suggest the unexplored Hellas Planitia, or plain, and Jezero crater on the northwest rim of Isidis Planitia, where Nasa’s Perseverance rover is collecting rocks to return to Earth in a decade.
Next on Sauterey’s to-do list: investigate the possibility that microbial life could still exist deep within Mars.
“Could Mars still be inhabited today by micro-organisms from this primitive biosphere? he said. “If so, where? »
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