Mars’ organic carbon may have originated from a series of electrochemical reactions between briny liquids and volcanic minerals, according to analyses of three Martian meteorites. The discovery that natural systems can form a small corrosion-powered battery that drives electrochemical reactions between minerals and surrounding liquid has major implications for astrobiology. A similar process could occur anywhere that igneous rocks are surrounded by brines, including the subsurface oceans of Jupiter’s moon Europa and Saturn’s moon Enceladus.