Jupiter’s Moon Ganymede
Not to be outdone by its Jovian sibling, Ganymede, the largest of Jupiter’s moons, also appears to host a hidden ocean world. Back in 2015, NASA scientists documented strange rocking motions in the moon, which they took as evidence of a substantial subterranean ocean. Calculations point to an ocean 60 miles (100 km) deep, pointing to a tremendous amount of liquid water on this oversized moon. For reference, oceans on Earth get no deeper than 6 miles (10 km).
