Saturn

Saturn is probably the best known, and most beautiful planet in the Solar System. Like Jupiter, Saturn is composed mostly of hydrogen. But in contrast to the vivid colours and wild turbulence found in Jovian clouds, Saturn's atmosphere has a more subtle, butterscotch hue, and its markings are muted by high-altitude haze. While its possession of a ring system it not unique, it has a set of rings which are far more extensive and more easily seen than any other planet. It is this ring system that makes Saturn so beautiful. Saturn is the second largest planet in the solar system with a diameter of 120,000 kilometres. It orbits the Sun every 30 years at a distance about ten times that of the Earth. The shape of the planet is a markedly oblate spheroid with a polar diameter some ten per cent smaller than that at the equator. Saturn is the least dense of all the planets, its mean density being only 0.7 times that of water and its volume would enclose more than 750 Earth's. Even so, its mass is only 95 times that of Earth; with a density less than that of water, it would float in an ocean if there were one big enough..

The visits by the Voyager spacecraft revised almost all that we know about Saturn, its rings and its satellites. Three American spacecraft have visited Saturn. Pioneer 11 sped by the planet and its moon Titan in September 1979, returning the first close-up images. Voyager 1 followed in November 1980, sending back breathtaking photographs that revealed for the first time the complexities of Saturn's ring system and moons. Unlike rocky inner planets such as Earth, Saturn and the other gas giants have no surface on which to land. A spacecraft pilot foolhardy enough to descend into its atmosphere would simply find the surrounding gases becoming denser and denser, the temperature progressively hotter; eventually the craft would be crushed and melted.

A large, modern telescope will reveal Saturn banded in pale yellow and grey; photos from the Voyager 1 and 2 spacecraft that flew by Saturn in the early 1980s showed even more detail in the cloud tops of its upper atmosphere.

Saturn has 18 named satellites, more than any other planet. In addition, many more have been reported and given provisional designations.