Saturn

Perhaps the most beautiful of all the planets, Saturn's pale butterscotch atmosphere is surrounded by the elegant and intriguing ring system, held in suspension by the invisible strings of gravity. Although they appear solid, the rings are actually made up of countless small particles of ice, ranging in size from tiny snowflakes to huge icebergs the size of a house. Despite its enormous width (more than 400,000 kilometres across), the rings measure only a few metres from top to bottom. Close observations of the rings show that the three main bands are actually made up of huge numbers of smaller concentric rings, dividing and sub-dividing almost without limit.

Closer scrutiny of Saturn's rings reveals dark, radial markings which move around the plane of the rings like spokes about the hub of a wheel. These bizarre features are caused by small dust-like particles which become electrically charged as a result of collisions with energetic electrons. The electromagnetic forces levitate the particles above the rings and the spokes are swept around Saturn by its rotating magnetic field.

The planet itself, despite its differing appearance shares much in common with its larger cousin, Jupiter. Both have rapid spins of around 10 hours and are largely composed of hydrogen and helium with small amounts of elements like ammonia. Both planets appear to have their own internal heat sources, relics from the days of their formation. Visually Saturn appears more tranquil than the raging surface of Jupiter, but in fact the wind speeds are greater, reaching as high as 1800 kilometres per hour. Despite Saturn's enormous size and mass, Saturn is the planet with the lowest average density. In fact if a large enough ocean of water could be found, Saturn would float on the surface. This is because hydrogen and helium are the two lightest elements.

Saturn has at least 17 satellites, many of which have peculiar and unique properties. The surface of Iapetus is acutely divided. One hemisphere shines as bright as ice, the other half is as dark as coal. Titan has a substantial atmosphere, which may be hiding oceans of methane. Mimas has a surface covered with impact craters, dominated by the enormous crater Herschel, so large it must have almost destroyed the moon. Janus and Epimetheus are Saturn's two co-orbiting satellites. Every four years they barely avoid a collision by switching places, following the other moon's orbit until their next meeting. Saturn also has a pair of shepherd moons, which orbit on either side of a narrow outer ring, holding the material in place.