very old Mars French scientists reported today, Monday, that an environment capable of harboring an underground world teeming with microscopic organisms. The researchers concluded that if they existed, these simple life forms would have altered the atmosphere so profoundly that it unleashed the Martian ice age and annihilated itself.
The results offer a bleak view of the ways in the universe. Life – even life as simple as microbes – “may in fact commonly cause its own demise,” said the study’s lead author, Boris Souteri, now a postdoctoral researcher at the Sorbonne.
The results are “a little bleak, but I think they’re also very motivating,” he said in an email. “They challenge us to rethink the way the biosphere and its planet interact.”
In a study published in Nature Astronomy, Soteri and his team said they used climate and terrain models to assess the habitability of Mars’ crust 4 billion years ago, when the Red Planet was thought to be water-filled and more hospitable than today.
They speculated that methane-producing microbes devouring the hydrogen might have thrived below the surface at the time, with several inches (a few tens of centimeters) of dirt more than enough to protect them from the harsh radiation incoming. According to Souteri, anywhere on Mars free of ice would have been teeming with these creatures, just as it did on early Earth.
Soteri said the supposedly warm, humid climate of early Mars would have been compromised by the uptake of too much hydrogen from the thin, carbon dioxide-rich atmosphere. With temperatures dropping by nearly -400 degrees Fahrenheit (-200 degrees Celsius), any organism at or near the surface would likely have gone deep in an attempt to survive.
By contrast, the researchers said, microbes on Earth may have helped maintain temperate conditions, given the nitrogen-dominated atmosphere.
SETI’s Kaveh Pahelvan said future models of the Martian climate need to be studied by the French research.
Pahlivan led a separate recent study suggesting that Mars was born humid with warm oceans lasting for millions of years. His team concluded that the atmosphere would have been dense and was mostly hydrogen at the time, acting as a heat-trapping greenhouse gas that was eventually transported to higher altitudes and lost to space.
Pahlifan said the French study investigated the climatic effects of potential microbes when carbon dioxide dominated the Martian atmosphere, and thus not applicable to earlier times.
“What their study shows is that if (this) life existed on Mars” during this earlier period, he added in an email, “it would have had a significant impact on the prevailing climate.”
Best places to look for traces of this past life? French researchers suggest the undiscovered Hellas Planet crater, or plain, and Jezero crater on the northwest edge of Isidae Planetia, where NASA’s Perseverance rover is collecting rocks to bring them back to Earth within a decade.
Next up on Sautere’s mission list: researching the possibility of microbial life continuing deep in Mars.
Could Mars today be inhabited by microorganisms descending from this primitive biosphere? He said. “If so where?”
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