Newly Discovered Carbon on Mars: Origin May Be Biologically Produced Methane

"NASA’s Curiosity rover landed on MarsMars is the second smallest planet in our solar system and the fourth planet from the sun. Iron oxide is prevalent in Mars' surface resulting in its reddish color and its nickname "The Red Planet." Mars' name comes from the Roman god of war." style="margin: 0px; padding: 0px; border-top: 0px; border-right: 0px; border-left: 0px; border-image: initial; font: inherit; vertical-align: baseline; border-bottom: 1px dotted rgb(0, 0, 0) !important;">Mars on August 6, 2012, and since then has roamed Gale Crater taking samples and sending the results back home for researchers to interpret. Analysis of carbon isotopes in sediment samples taken from half a dozen exposed locations, including an exposed cliff, leave researchers with three plausible explanations for the carbon’s origin — cosmic dust, ultraviolet degradation of carbon dioxide, or ultraviolet degradation of biologically produced methane. 

The researchers note today (January 17, 2022) in Proceedings of the National Academy of Sciences that “All three of these scenarios are unconventional, unlike processes common on Earth.”
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“All three possibilities point to an unusual carbon cycle unlike anything on Earth today,” said House. “But we need more data to figure out which of these is the correct explanation. It would be nice if the rover would detect a large methane plume and measure the carbon isotopes from that, but while there are methane plumes, most are small, and no rover has sampled one large enough for the isotopes to be measured.”

House also notes that finding the remains of microbial mats or evidence of glacial deposits could also clear things up, a bit.

“We are being cautious with our interpretation, which is the best course when studying another world,” said House.

Curiosity is still collecting and analyzing samples and will be returning to the pediment where it found some of the samples in this study in about a month.

“This research accomplished a long-standing goal for Mars exploration,” said House. “To measure different carbon isotopes — one of the most important geology tools — from sediment on another habitable world, and it does so by looking at 9 years of exploration.”