A new map of Mars reveals the abundance of aqueous minerals—clays and salts that form in the presence of water—that were created during the planet’s distant watery past. “The big surprise is the prevalence of these minerals. Ten years ago, planetary scientists knew of around 1000 outcrops on Mars. This made them interesting as geological oddities. However, the new map has reversed the situation, revealing hundreds of thousands of such areas in the oldest parts of the planet.”