We might not be the first lifeforms in the solar system to face climate change caused by our own activities. A new model suggests that ancient Mars was once habitable enough for methane-producing microbes, who may have wiped themselves out by destroying the planet’s atmosphere irreparably.
Modern Mars has a very thin atmosphere and is extremely cold and drier than any desert on Earth. There was once no river, delta, lake, or ocean in the area – decades of observations from rovers and orbiters have provided evidence to the contrary. With that in place, microscopic life should have been able to survive.
Using a computer model of ancient Mars’ crust, atmosphere, and climate, researchers from the University of Arizona conducted a new study. Additionally, they explored whether methanogens could survive in the ecosystem, and how their presence might change it. Methanogens consume carbon dioxide and hydrogen and produce methane.
“Once we had produced the model, we put it to work – metaphorically speaking,” said Boris Sauterey, the study’s first author. As a result, we were able to determine the likelihood of a Martian underground biosphere. If such a biosphere existed, it would have altered the chemistry of the Martian crust, and it would have also impacted the atmosphere’s chemical composition.”
Indeed, microbes flourished on early Mars not only because they could survive, but also because they could survive. Approximately a few hundred meters below the surface, their comfort level would be greatest.
Researchers modified the model next to simulate how the microbes may have affected the ecosystem. They were surprised to discover that their reign was relatively short-lived. A global cooling event could occur as soon as a few hundred thousand years after the microbes removed too much hydrogen from the atmosphere and replaced it with methane.
“These microbes would have faced the problem that Mars’ atmosphere had basically vanished, completely thinned out, so their energy source would have vanished and they would have had to find another source of energy,” Sauterey said. Additionally, the temperature would have dropped, and they would have had to go much deeper into the crust. Presently, it is impossible to predict how long Mars would have been habitable.”
Although the story is intriguing, we aren’t sure if it is true. Microbial life could have existed on Mars if the conditions were right, but no evidence has been found that it existed so far. That’s one of the main jobs of Perseverance, which is currently searching for signs of life in a promising river delta. Some scientists believe some of these deep-dwelling microbes may still be alive.