Underground microbes ‘may have swarmed on ancient Mars’

A climate change on Mars caused by ancient microbes may have led to their extinction, according to a new climate modeling study.

The study found that simple microbes that eat hydrogen and excrete methane could be living on Mars around 3.7 billion years ago. This was at the same time primitive life was beginning to take root on Earth. According to a team led by Boris Sauterey, an astrobiologist from the Institut de Biologie de l’Ecole Normale Superieure in Paris, France, the emergence of simple life created an environment that was conducive to the development of more complex life forms.

Sauterey’s team performed a complex computer modeling study to simulate the interaction between what we know about Mars’ ancient environment and the lithosphere. They also simulated hydrogen-consuming microbes that were similar to those found on Earth. Researchers discovered that Mars was cooled by methane from the microbes, which, unlike Earth, gradually warmed it.

The effect of greenhouse gases can be reduced

Sauterey stated that Mars at that time would have been wet and warm. This is between minus 10 and 20 degrees Celsius (14 degrees Fahrenheit and 64 degrees Fahrenheit). It had rivers, lakes, and possibly oceans of liquid water on its surface. Its atmosphere was very different from that of Earth. It was just as dense, but it had more hydrogen and carbon dioxide, which were both potent warming gases.

Mars is a much cooler planet than Earth, and so it needs greenhouse gases to keep its temperature stable. However, as the early microbes began to consume hydrogen and produce methane (which is a potent greenhouse gas on Earth), this warming caused Mars to become increasingly inhospitable.

Sauterey explained that hydrogen was an extremely potent warming gas on ancient Mars because of what we call the collision-induced absorb effect, where molecules of hydrogen and carbon dioxide interact with one another. We don’t see this on Earth, as our atmosphere isn’t as rich in carbon dioxide as Mars’. The microbes effectively replaced hydrogen, a stronger warming gas, with methane (which would have had a net cooling impact).

Hidden deep

As the planet cooled, more of its water became ice. The surface temperature fell below minus 70 degrees Fahrenheit (minus sixty degrees Celsius). This forced the microbes to go deeper into the crust, where there were still warmer conditions. The modeling showed that the microbes lived initially directly below the Martian sandy surface and were able to escape to depths greater than 0.6 miles (1 km) over the next few hundred million years.

Sauterey’s team found three places where ancient microbes could have survived near the surface. These three locations are Jezero Creator where NASA’s Perseverance Rover is currently searching for rock samples that might contain traces of ancient life. Also, two low-lying plains were identified: Hellas Planitia, at the mid-latitudes of the southern hemisphere, and Isidis Planitia, just north of Mars’s equator.

Sauter stated that the areas where microbes are closest to the surface of the planet would be the warmest. “And the deepest areas are often the warmest.” The climate at the bottom of these valleys and craters is warmer than the rest of the world, so it’s easier to find evidence of these life forms there.

Oasis for livability

The researchers want to determine if these ancient microbes are still living in Mars’ crust. Although satellites have detected methane traces in Mars’ thin atmosphere previously, it is not yet possible to determine if this methane is biologically derived.

Sauterey stated that the Martian atmosphere has largely disappeared these days and these microbes would need to find another source of energy. “We can see that a geological process on Mars could provide the same kind of energy substrate, hydrogen, and carbon dioxide that these microbes could rely on.” We’d like to know more about that and locate any possible oases of habitability within the Martian crust.

Are you a self-destructive person?

Sauterey said that the findings suggest that life may not possess the self-sustaining qualities some biologists believed it had on Earth (until the advent of humankind). In fact, life may just be spontaneously emerging in the universe and then becoming extinct from its interaction with the host planet.

Sauterey stated that “the ingredients of life are everywhere in this universe.” It is possible for life to appear regularly in the universe. However, the inability of life to sustain habitable conditions on the planet’s surface makes it disappear very quickly. This experiment shows that even the most primitive biosphere can have an entirely self-destructive effect.

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