According to French scientists, ancient Mars may have had an environment capable of supporting an underground world teeming with microscopic organisms. The researchers concluded that if these simple life forms existed, they would have altered the atmosphere so profoundly that they would have triggered a Martian Ice Age and suffocated themselves.
The findings paint a bleak picture of the universe’s workings. Boris Sauterey, now a post-doctoral researcher at Sorbonne University, said that life—even simple life like microbes—”might actually commonly cause its own demise.”
The results “are a bit gloomy, but I think they are also very stimulating.,” he said in an email. “They challenge us to rethink the way a biosphere and its planet interact.”
In a study in the journal Nature Astronomy, Sauterey and his team said they used climate and terrain models to evaluate the habitability of the Martian crust some 4 billion years ago when the red planet was thought to be flush with water and much more hospitable than today.
The findings paint a bleak picture of the universe’s workings. By contrast, microbes on Earth may have helped maintain temperate conditions, given the nitrogen-dominated atmosphere.Boris Sauterey
They hypothesized that hydrogen-gobbling, methane-producing microbes could have thrived just beneath the surface back then, with several inches (a few tens of centimeters) of dirt protecting them from harsh incoming radiation. According to Sauterey, these organisms could have swarmed anywhere on Mars that was free of ice, just as they did on early Earth.
The early Mars’ presumably moist, warm climate, however, would have been jeopardized by so much hydrogen sucked out of the thin, carbon dioxide-rich atmosphere, according to Sauterey. As temperatures dropped to nearly minus 400 degrees Fahrenheit (minus 200 degrees Celsius), any organisms on or near the surface would have buried deeper in an attempt to survive.
By contrast, microbes on Earth may have helped maintain temperate conditions, given the nitrogen-dominated atmosphere, the researchers said.
The SETI Institute’s Kaveh Pahlevan said future models of Mars’ climate need to consider the French research. Pahlevan led a separate recent study suggesting Mars was born wet with warm oceans lasting millions of years. The atmosphere would have been dense and mostly hydrogen back then, serving as a heat-trapping greenhouse gas that eventually was transported to higher altitudes and lost to space, his team concluded.
The French study investigated the climate effects of possible microbes when Mars’ atmosphere was dominated by carbon dioxide and so is not applicable to the earlier times, Pahlevan said.
“What their study makes clear, 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.
What are the best places to look for traces of this previous life? The unexplored Hellas Planita, or plain, and Jezero Crater on the northwestern edge of Isidis Planita, where NASA’s Perseverance rover is currently collecting rocks for return to Earth in a decade, are suggested by the French researchers.
Sauterey’s next task is to investigate the possibility of microbial life still existing deep within Mars. “Could microorganisms descended from this primitive biosphere still inhabit Mars today?” he wondered. “And if so, where?”