A new climate modeling study has found that ancient microbes caused a climate change on Mars that made the planet less habitable, which may eventually lead to its extinction.
According to the study, simple microbes that feed on hydrogen and excrete methane can thrive Mars About 3.7 billion years ago, around the same time that primitive life was taking hold a landPrimordial oceans. But while the appearance simple life It gradually created an environment conducive to more complex life forms, and just the opposite has happened on Mars, according to a team of scientists led by astrobiologist Boris Souteri of the Institut Biologie de l’Ecole Normale Supérieure (IBENS) in Paris, France.
Sutri and his team conducted a complex computer modeling study that simulates the interaction of what we know about the ancient atmosphere The Martian lithosphere with hydrogen-consuming microbes similar to those found on ancient Earth. The researchers found that while the methane produced by these microbes on Earth is gradually warming the planet, Mars is cooling instead, forcing the microbes into deeper and deeper layers of the planet’s crust to survive.
Related: NASA’s Mars Life Explorer mission will dig deep to search for life on the Red Planet
slow down the greenhouse effect
“At that time, Mars was relatively humid and relatively warm, between minus 10 and 20 degrees Celsius. [14 degrees Fahrenheit and 68 degrees Fahrenheit], “Suteri for Space.com.” It contained liquid water in the form of rivers, lakes, and possibly oceans on its surface. But its atmosphere was completely different from that of the Earth. It was dense, but richer in carbon dioxide and hydrogen, both of which were powerful heating gases.”
to be away from the sun From Earth, and therefore naturally cooler, Mars needed greenhouse gases to maintain a comfortable temperature for life. But when those early microbes started devouring hydrogen and producing methane (which on Earth acts as a potent greenhouse gas), they actually slowed that warming. Global Warmingwhich gradually makes ancient Mars so cold that it becomes inhospitable.
“In ancient Mars, hydrogen was a very powerful heating gas because of something we call the impact-induced sorption effect where carbon dioxide and hydrogen molecules interact with each other,” Souteri explained. “We don’t see that on Earth because our planet’s atmosphere isn’t as rich in carbon dioxide as Mars once was. So basically microbes have replaced a more potent greenhouse gas, hydrogen, with a less potent heating gas, methane, which had a net cooling effect.”
hiding deeper
As the planet cooled, more of its water turned into ice and the surface temperature dropped below 70 degrees Fahrenheit (below 60 degrees Celsius), pushing the microbes deeper and deeper into the crust where warmer conditions persisted. Modeling revealed that while the microbes initially may have lived comfortably just below the sandy surface of Mars, within a few hundred million years they were forced to retreat to depths of more than 0.6 miles (1 kilometer).
Sotteri and his team have identified three sites where traces of these ancient microbes are most likely to have survived near the surface. These sites include Jezero Craterwhere NASA’s Perseverance Vehicle He is currently searching for rock samples that could harbor traces of this ancient life, and two lower plains: Hellas Planitia in the mid-latitudes of the Southern Hemisphere, and Isidis Planitia north of the Martian equator.
“The places on the planet where those microbes would have been closest to the surface are the warmer regions,” Sutri said. “And usually the warmest places are the ones that are the deepest. At the bottom of these craters and valleys, the climate is much warmer than the rest of the surface, so it would be much easier to look there for evidence of these life forms.”
oasis of residence
Next, the researchers want to see if these ancient microbes still live anywhere within the crust of Mars. Satellites have been detected by Traces of methane in the thin atmosphere of MarsHowever, it is currently impossible to determine whether this methane is of biological origin.
“Because the Martian atmosphere has mostly disappeared these days, these microbes will have to switch to another source of energy,” Souteri said. “We can imagine that some geological processes on Mars today could provide the same kind of active substrate, hydrogen and carbon dioxide, that these microbes can live on. We’d like to find out and try to localize any potential habitable oases in the Martian crust.”
Is life self destructive?
Souteri added that the findings suggest that life may not have self-sustaining traits as some biologists on Earth believed (until the advent of humanity). In fact, life may appear randomly in Universeonly to become extinct through its interaction with the host world.
“The ingredients for life are everywhere in the universe,” said Souteri. “So it is possible that life appears regularly in the universe. But the inability of life to maintain habitable conditions on the planet’s surface is causing it to become extinct very quickly. Our experiment takes it a step further because it shows that even a very primitive biosphere can have a completely self-destructive effect.”
the study (Opens in a new tab) It was published in Nature Astronomy on Monday (10 October).
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