Earthly penny used as scale in Curiosity’s Martian rock photos

NASA's Curiosity rover photographed a real penny on Mars with its MAHLI camera. The coin, which traveled to Mars with the rover, sits dusty on the Martian surface, and its true purpose is to provide a known-size reference for scale in geology photos, helping scientists gauge rock features. The penny was minted in 1909 and has accumulated dust during the mission's time on Mars.