If there ever was life on Mars—and that’s a huge «if»—conditions during the planet’s infancy most likely would have supported it, according to a study led by University of Arizona researchers.
October 16, 2022
If there ever was life on Mars—and that’s a huge «if»—conditions during the planet’s infancy most likely would have supported it, according to a study led by University of Arizona researchers.
Dry and extremely cold, with a tenuous atmosphere, today’s Mars is extremely unlikely to sustain any form of life at the surface. But 4 billion years ago, Earth’s smaller, red neighbor may have been much more hospitable, according to the study, which is published in Nature Astronomy.
Most Mars experts agree that the planet started out with an atmosphere that was much denser than it is today. Rich in carbon dioxide and hydrogen, it would have likely created a temperate climate that allowed water to flow and, possibly, microbial life to thrive, according to Regis Ferrière, a professor in the UArizona Department of Ecology and Evolutionary Biology and one of two senior authors on the paper.
The authors are not arguing that life existed on early Mars, but if it did, Ferrière said, «our study shows that underground, early Mars would very likely have been habitable to methanogenic microbes.»
Such microbes, which make a living by converting chemical energy from their environment and releasing methane as a waste product, are known to exist in extreme habitats on Earth, such as hydrothermal vents along fissures in the ocean floor. There, they support entire ecosystems adapted to crushing water pressures, near-freezing temperatures and total darkness.
The research team tested a hypothetical scenario of an emerging Martian ecosystem by using state-of-the-art models of Mars’ crust, atmosphere and climate, coupled with an ecological model of a community of Earthlike microbes metabolizing carbon dioxide and hydrogen.
On Earth, most hydrogen is tied up in water and not frequently encountered on its own, other than in isolated environments such as hydrothermal vents. Its abundance in the Martian atmosphere, however, could have provided an ample supply of energy for methanogenic microbes about 4 billion years ago, at a time when conditions would have been more conducive to life, the authors suggest. Early Mars would have been very different from what it is today, Ferrière said, trending toward warm and wet rather than cold and dry, thanks to large concentrations of hydrogen and carbon dioxide—both strong greenhouse gases that trap heat in the atmosphere.
«We think Mars may have been a little cooler than Earth at the time, but not nearly as cold as it is now, with average temperatures hovering most likely above the freezing point of water,» he said.
