Ancient Microbes Triggered Climate Change, Killed All Life on Mars

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New climate modeling research reveals that the extinction of ancient bacteria on Mars may have been caused by a shift in temperature that rendered the planet less habitable.

The research suggests that basic hydrogen-eating methane-excreting bacteria might have flourished on Mars about 3.7 billion years ago, at the same time that early life was establishing itself in Earth’s primordial seas. However, a team of scientists headed by astrobiologist Boris Sauterey from France’s Institut de Biologie de l’Ecole Normale Supérieure (IBENS) found that the reverse occurred on Mars, with the appearance of primitive life not at all paving the way for the development of more sophisticated life.

New modeling

Using sophisticated computer modeling, Sauterey and his colleagues investigated how hydrogen-consuming bacteria comparable to those that existed in Earth’s ancient past would have interacted with the planet’s old atmosphere and lithosphere. Scientists discovered that whereas the methane created by these bacteria steadily warmed the Earth, the opposite occurred on Mars, forcing the microbes to retreat further and deeper into the planet’s crust in order to live.

Mars, which is farther from the sun and so inherently colder than Earth, needs those greenhouse gasses to sustain a tolerable temperature for life. This warming greenhouse effect was delayed when early bacteria began consuming the hydrogen and releasing methane, eventually cooling ancient Mars to an uncomfortable degree.

The bacteria were forced further and deeper into the crust, where temperatures remained above minus 70 degrees Fahrenheit, as the planet chilled and more of its water turned into ice, and the surface temperature plummeted below that threshold. The simulation showed that within a few hundred million years, the bacteria on Mars were forced to withdraw to depths of more than 0.6 miles, despite the fact that they may have originally lived contentedly just under the sandy surface.

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