Rings, Moons

December 17, 2004

This 1981 Voyager 2 image shows the vast Saturn ring system, as well
as three small icy satellites and the shadow of a fourth.

Saturn is
the second largest planet in the Solar System. It has a volume about
760 times that of Earth. Like Jupiter, Uranus, and Neptune, it has no
solid surface, but is instead an enormous sphere of gas which gradually
compresses into fluid at great depths beneath the clouds.

Most of the
visible markings are formed in a layer of ammonia ice clouds, which form
at a pressure level in Saturn's atmosphere that is comparable to sea-level
atmospheric pressure on Earth. Above those clouds, Saturn's atmosphere,
like those of the Sun and the other three gas giant planets, is composed
almost exclusively of hydrogen and helium. By contrast, Saturn's
rings and icy satellites appear to be composed primarily of water ice.
Image reprocessed by USGS. (P-43538)