NASA’s Curiosity rover has discovered siderite, a carbonate mineral, beneath Mars’ surface—providing new clues that the Red Planet may have once had conditions suitable for life billions of years ago.

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.