Traces of serpentine found at Nili Fossae on Mars.NASA/JPL/University of Arizona
Surprises keep coming from Nili Fossae, a long, deep scar in the surface of Mars. In December last year, scientists reported evidence there for carbonates — minerals that typically form in the presence of water1. Then, in January, reports came that there was a large plume of methane in the area. On Earth the gas is made mostly by animals as a by-product — although it can also be produced naturally in the absence of life2.
Now Bethany Ehlmann, a PhD student at Brown University in Providence, Rhode Island, is finding evidence at Nili Fossae for a mineral that could tie all these observations together. Ehlmann used a spectrometer on the Mars Reconnaissance Orbiter to identify two small outcrops of a mineral called serpentine. Serpentine arises from another mineral, olivine, in a hydrothermal process in which hydrogen gas is produced — a potential energy source for microbes that could in turn produce methane.
The process of serpentinization also produces methane itself, without the need for life. "It was a past source of methane, for sure," says Ehlmann, who announced the result on Wednesday at the Lunar and Planetary Science Conference at The Woodlands, near Houston, Texas. Serpentine can also be altered, in lower temperature water, into carbonate.
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