NASA’s Juno spacecraft has discovered that Jupiter’s moon, Ganymede, has organic compounds and salt on its icy surface. Taking a closer look at these substances, scientists have discerned the ingredients of the moon’s materials include sulfur compounds such as sulfurous acid, and chloride salts like magnesium chloride and sodium chloride. The discovery of these salts and organics suggests the moon may have once had a subsurface ocean over its history. With more future studies, scientists hope to understand the moon’s evolution and its hidden ocean better.