The largest moon in our solar system 
may be hiding an ocean, according to NASA and ESA's Hubble team. So you can add Jupiter's Ganymede to 
Europa, 
Enceladus, and others on the ever-growing list of bodies in our solar system 
that might be home to water and 
good candidates for finding extraterrestrial life.
The researchers here focused in on an aurora phenomenon on the surface of Ganymede, one of the four large 
Galilean moons of Jupiter. Scientists 
had long suspected a subterranean ocean on Ganymede, the 
aurora displayed signs of a large amount of salt water under the surface of the moon—the first solid evidence of the ocean. The team spotted the phenomenon by imaging the moon in the ultraviolet spectrum.