In the wisp-thin sky of Ganymede, the largest satellite in the Solar System, astronomers have detected evidence of water vapour for the first time. The discovery could shed light on similar watery atmospheres that may envelop other icy bodies in the Solar System and beyond.
Previous research suggested that Ganymede – which is larger than Mercury and Pluto and only slightly smaller than Mars – may contain more water than all of Earth’s oceans. However, the Jovian moon is so cold that water on its surface is frozen. Any liquid water would lurk about 100 miles below its crust.