The Curiosity rover at the Windjana outcrop on Mars, where it found evidence of mangnese oxide on rocks and in rock fissures. The mineral is formed only in the presence of water and plentiful oxygen. (NASA)
Early in the Curiosity rover’s trek across Gale Crater on Mars, team member and Los Almos National Laboratory planetary scientist Nina Lanza reported finding surprisingly high concentrations of the mineral manganese oxide. It was showing up as a blackish-purple fill to cracks in rocks, and possibly as a surface covering to others.
Lanza, who had some experience with the common and much-debated mineral– found in the American Southwest and other arid climes — initially proposed that it just might be related to terrestrial rock varnishes. This was a bold proposal because manganese-oxide rock varnishes on Earth are almost always associated with microbes, which are known to concentrate the mineral. So was this a biosignature coming from Mars?
Two years later, Lanza and others on the Curiosity team have published a paper describing in detail the regular detection of Martian manganese oxide, sometimes in concentrations higher than what is found on Earth. Based on the surrounding geology and geochemistry, the team then concluded that when ...