Past life on Mars could explain the low levels of carbon-13

After a decade examining the Martian surface, the Curiosity rover has now given an insight into the life of carbon on ancient Mars, hinting at which geological – and perhaps even biological – processes shaped the planet.

The rover has been measuring the ratio of carbon-12 to carbon-13 on the planet, a value set during the Solar System’s creation, but which changes over time due to all manner of geological, biological and cosmic processes. Curiosity found several areas of depleted carbon-13. There are three possible explanations: Mars passed through a Galactic cloud which deposited the carbon; ultraviolet radiation broke apart carbon dioxide in the atmosphere; or, ancient microbes produced and consumed methane.

“All three possibilities point to an unusual carbon cycle, unlike anything on Earth today,” says Christopher House from Penn State University, who led the study. “But we need more data to figure out which of these is the correct explanation.” www.psu.edu