Space

Ancient Martian life may have died out in self-induced climate change

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An artist's impression of a hypothesized watery ancient Mars
ESO/M. Kornmesser
An artist's impression of a hypothesized watery ancient Mars
ESO/M. Kornmesser
The team's models of Mars undergoing glaciation as a result of microbes altering the atmosphere
Boris Sauterey and Regis Ferrière

Humans might not be the first lifeforms in the solar system to face the threat of their own activity changing the climate of their home planet. A new model suggests that ancient Mars was once habitable enough to support methane-producing microbes, and they may have wiped themselves out by causing irreparable damage to the Red Planet’s atmosphere.

Modern Mars is extremely cold and drier than any desert on Earth, with a very thin atmosphere. But this wasn’t always the case – decades of observation from rovers and orbiters have turned up quite clear and extensive evidence of ancient rivers, deltas, lakes, and possibly even oceans. And with that, conditions should have been habitable to microscopic life.

For the new study, researchers at the University of Arizona modeled ancient Mars, including its crust, atmosphere and climate. Most importantly, they added an ecological model of methanogens – microbes that consume carbon dioxide and hydrogen and produce methane – and investigated whether the conditions would allow them to survive, and what effects they might have on the ecosystem.

"Once we had produced our model, we put it to work in the Martian crust – figuratively speaking," said Boris Sauterey, first author of the study. "This allowed us to evaluate how plausible a Martian underground biosphere would be. And if such a biosphere existed, how it would have modified the chemistry of the Martian crust, and how these processes in the crust would have affected the chemical composition of the atmosphere.”

And sure enough, the team found that microbes could not only survive but thrive on early Mars. The simulation showed that they would be most comfortable within the first few hundred meters below the surface.

The team's models of Mars undergoing glaciation as a result of microbes altering the atmosphere
Boris Sauterey and Regis Ferrière

Next, the researchers modified their model to simulate what kind of feedback the microbes might have had on the ecosystem. And to their surprise, they found that their reign may have been relatively short-lived. The microbes would have removed too much hydrogen from the atmosphere and replaced it with methane, triggering a global cooling event within as little as a few hundred thousand years.

"The problem these microbes would have then faced is that Mars' atmosphere basically disappeared, completely thinned, so their energy source would have vanished and they would have had to find an alternate source of energy,” said Sauterey. "In addition to that, the temperature would have dropped significantly, and they would have had to go much deeper into the crust. For the moment, it is very difficult to say how long Mars would have remained habitable."

As intriguing as the story is, we don’t yet know that this is what actually happened. Evidence abounds that the conditions were right for microbial Martian life, but so far no evidence has been found that it existed. Thankfully, that’s one of the main jobs of the Perseverance rover, which is currently scouring a promising river delta in the search for signs of life. Other scientists believe there's a chance that some of these deep-dwelling microbes could still be alive today.

The research was published in the journal Nature Astronomy.

Source: University of Arizona

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8 comments
Rustgecko
Total speculation passing off as science. It would be interesting to know how many hundreds of simulations they did that did not produce this result.
aksdad
Interesting, but our faith in simplified computer simulations of incredibly complex interactions is naive. Humans decide which variables they think are the most significant to include in the simulation, often with sparse evidence to support a hypothesis, then attempt to mathematically represent the influences the many selected variables have on the output. When trying to model a dynamic, nonlinear, chaotic system like planetary climate it's an impossible task with the current (lack of) understanding of all the factors and (lack of) computing power. Look at the wide range of estimates of temperature from the CMIP climate models for Earth's climate based on the hypothesis that CO2 (and methane) are the main drivers of recent, moderate temperature increases (~1° C) over the last century and the huge differences (>100%) between predictions and measured trends.
Kenneth Nemchak
Just stop. You're making clowns out of yourselves.
Catweazle
It should be remembered that the first organisms on the Earth when it had a very CO2-rich atmosphere were anaerobic life forms that that exhaled oxygen, thus producing an oxygen-rich environment that was more suitable to oxygen-dependent organisms that replaced them at the top of the life form pyramid.
Kyle Thomas
So ancient Martian life caused their planet's magnetosphere to disappear? That's some extreme climate change. That's not even something we're capable of yet.
Nobody
I agree with the skepticism of the other commenters. Models can be made to verify any results that you can preconceive. They are NOT proof of anything. Nor do statistics purify bad data. I forget who said there are lies, d###ed lies, and statistics but it was an accurate observation. Even in the 1960s astronomers knew that Mars weak gravity and apparent lack of a magnetic field would not allow it to hold anything more than a rare atmosphere. Mars has already been Terra formed by time to be what it currently is. It's humorous to hear people talk of making it a viable planet for colonization. If we can't preserve Earth 1.0, we sure can't make Mars an earth 2.0.
NMBill
The operative words here are "may have . . ." Whenever this formulation is used, the obverse is also applicable: "may not have . . ."
Alan Reyes
Organism induced climate change is by no means first done by humans..if humans do it at all.
The first true organizm climate change was the one that changed the Earth to an oxygen atmosphere, which was a true climate change. Most organizms create at least some microclimate around themselves so it is common for life to affect the climate.