In those drill sites, Curiosity detected deposits containing an iron carbonate material called siderite. According to Ben Tutolo, a University of Calgary associate professor of Earth, Energy, and Environment Studies as well as a NASA Mars Science Laboratory Curiosity Rover team, the data marks a major moment in the search for extraterrestrial life.

To study Mars’s chemical and mineral makeup, the Curiosity rover drills one to 1.5 inches down into the subsurface, then drops the powdered rock samples into an instrument in its belly called CheMin. The instrument, developed at NASA’s Ames Research Center in California’s Silicon Valley, uses X-ray diffraction to analyze rocks and soil.

A treasure trove of clues from Curiosity reveals that ancient Mars once trapped massive amounts of CO2 in its crust, thanks to surprising concentrations of iron carbonate deep in Gale Crater. By drilling into layers laid down in a vanished lake,