Rocks on the surface of Mars have yielded the best clue yet that the planet once had an atmosphere rich in oxygen.
Mars owes its sobriquet “the Red Planet” to the abundance of iron oxide, otherwise known as rust, on its surface. But in addition to all that iron, NASA’s Curiosity rover has now found substantial amounts of manganese oxide in rocks in Mars’s Gale crater.
“We found 3 per cent of rocks have high manganese oxide content,” Agnès Cousin of the Research Institute in Astrophysics and Planetology in Toulouse, France, told the European Geophysical Union meeting in Vienna, Austria, earlier this week. “That requires abundant water and strongly oxidising conditions, so the atmosphere may have contained much more oxygen than we thought.”
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