Ancient Martian life may have created the conditions for its own extinction

Ancient microbes on Mars likely triggered a climate change that led to their own demise, a report from Space.com explains.

The study was published in Nature Astronomy, and it details how simple microbes that fed on hydrogen and excreted methane were likely abundant on Mars roughly 3.7 billion years ago. This was at approximately the same time that the earliest life was forming in Earth's oceans.

In a fascinating turn, Mars' life created an environment that was not conducive to the evolution of more complex life forms. At the same time, on Earth, a completely different story was unfolding. The new findings reveal a great deal about the tiny nuances that can drastically alter the habitability of a planet. They also point to new avenues of research in the search for extraterrestrial life.

Simulating ancient life on Mars

The team behind the new paper, led by astrobiologist Boris Sauterey from the Institut de Biologie de l'Ecole Normale Supérieure (IBENS) in Paris, France, conducted complex computer simulations to reach their results.

Their computer models simulated the ancient atmosphere and lithosphere of Mars while adding hydrogen-consuming microbes similar to those found on Earth at the earliest stage of evolution on the planet. Ultimately, the scientists found that the same microbes that gradually produced methane on Earth to warm the planet actually cooled Mars instead. This drove them deep under the red planet's crust in search of warmth for survival.

Ancient Mars was richer in carbon dioxide and hydrogen than Earth, and it would have needed these warming gasses to form a habitable environment for early life forms. Instead, scientists believe the early microbes started stripping hydrogen from the atmosphere and replacing it with methane. This served to slow down the warming greenhouse effect required — especially as Mars is further from the Sun than the Earth and is naturally cooler. The result is that Mars' surface eventually became the inhospitable red wasteland we know today.

Speaking with Space.com, Sauterey explained how "on ancient Mars, hydrogen was a very potent warming gas because of something we call the collision-induced absorption effect where molecules of carbon dioxide and hydrogen interact with each other."

"We don't see that on Earth because our planet's atmosphere is not as rich in carbon dioxide as that of Mars used to be," they added. "So the microbes essentially replaced a more potent warming gas, hydrogen, with a less potent warming gas, methane, which would have had a net cooling effect."

Could life be self-destructive?

The study also explains how Mars's surface temperature will have dropped to below minus 70 degrees Fahrenheit (minus 60 degrees Celsius). This will have forced microbes on its surface to dig deeper and deeper into the red planet's crust, where the relative proximity to its mantle created warmer conditions.

Initially, the microbes will have been able to survive just below the Martian surface. Sauterey and his team have identified three locations where they believe Mars exploration missions may find traces of these ancient microbes. One of these locations is the ancient lakebed of the Jezero Crater, where NASA's Perseverance rover is currently looking for signs of ancient life. The other two are parts of the low-lying plains of Hellas Planitia and Isidis Planitia.

Not only does Sauterey and his team's study point toward specific locations to search for life on Mars, but they also point us toward a much bigger question about life throughout the universe. Namely, is life inherently self-destructive? Ancient microbes on Mars likely created the conditions that led to their own extinction. How many times might this scenario have played itself out throughout the cosmos?