Water is the most abundant compound in the universe; its composition consists of the 1st and 3rd most abundant elements, hydrogen and oxygen (helium is the 2nd most abundant element). Water in liquid form is common on Earth, but on other planetary bodies in the Solar System it is usually present as vapour or ice.
After the Solar System formed, most of the water was locked up as ice in the surface or interiors of the farthest planetary bodies. Earth actually has little water, comparatively, and what it does have is mostly on the surface.
Liquid water is also present as deep oceans on Europa and Titan, satellites of Jupiter and Saturn. The amount of liquid water on Mars and in Enceladus, a satellite of Saturn, could well be large.
This image is a comparison of the liquid water volume of Earth, Europa, and Titan to scale. Europa is estimated to have over two times and Titan nearly eleven times more liquid water than Earth has as subsurface oceans. Only liquid water is considered in these estimates though water ice is present in considerable amounts on Europa and Titan. The image assumes a mean ocean depth of 4 km, 100 km, and 200 km for Earth, Europa, and Titan, respectively.
After the Solar System formed, most of the water was locked up as ice in the surface or interiors of the farthest planetary bodies. Earth actually has little water, comparatively, and what it does have is mostly on the surface.
Liquid water is also present as deep oceans on Europa and Titan, satellites of Jupiter and Saturn. The amount of liquid water on Mars and in Enceladus, a satellite of Saturn, could well be large.
This image is a comparison of the liquid water volume of Earth, Europa, and Titan to scale. Europa is estimated to have over two times and Titan nearly eleven times more liquid water than Earth has as subsurface oceans. Only liquid water is considered in these estimates though water ice is present in considerable amounts on Europa and Titan. The image assumes a mean ocean depth of 4 km, 100 km, and 200 km for Earth, Europa, and Titan, respectively.
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