Water In The Outer Planets
When it comes to the existence of water in space, the moons of the outer Solar System planets seem to have the most activity. Take Europa, Jupiter’s sixth largest moon as an example. Europa has some similarities to Earth’s Moon including similar sizes and no atmosphere. Its distance from the Sun has left Europa with a surface of solid ice; scientist, however, believe that a liquid ocean is under the surface. In fact, it has been hypothesized that the liquid ocean of this smooth moon contains twice as much water as all the oceans and rivers of Earth combined. According to NASA, this ocean could be as much as 50 kilometers (31 miles) deep. Jupiter’s seventh moon, Ganymede, the largest moon in our Solar System and seventh moon of Jupiter is also thought to contain a hidden ocean of salty water.
As for the planet Saturn, it may only contain a trace amount of water. Its rings, however, are mostly composed of water ice. Saturn also has over 50 confirmed moons and most, if not all, contain water ice. The density of Rhea, Saturn’s second-largest moon, suggests that it is 75% water. The NASA's Cassini spacecraft, found that Titan, Saturn’s largest moon and the only known moon with an atmosphere, is likely to contain an ocean of ammonia and water deep within its dense surface. Enceladus, another of Saturn’s moon has water geysers that may be fed by underground water reservoirs.
Although not as much is known about the “ice giants" of Uranus and Neptune as the other planets, scientist do think they are composed of icy mantles, made up of water, ammonia and methane. Their moons also contain water. The inner moons of Uranus, for example, are roughly half water ice. Neptune’s major moon, Triton could also have a subsurface ocean.
Water, in some form or another, appears to be abundantly distributed in space. Trans-Neptunian objects in the Kuiper Belt, Oort Cloud and scattered disc all contain water ice.