Via Washington Post:
NASA announced evidence on Thursday that Jupiter's largest moon, Ganymede, has a saltwater ocean under its icy surface. The ocean seems to have more water than all the water on Earth's surface, according to new Hubble observations.
Scientists estimate that the ocean is 60 miles thick, which is about 10 times deeper than Earth's oceans. But unlike our salty waters, Ganymede's ocean is buried under 95 miles of ice.