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)