SATURN IS THE SIXTH PLANET from the Sun. It is a gas giant almost as big as Jupiter, with an equatorial diameter of about 75,000 miles (120,500 km). Saturn is thought to consist of a small core of rock and ice surrounded by an inner mantle of metallic hydrogen (liquid hydrogen that acts like a metal).
Outside the inner mantle is an outer mantle of liquid hydrogen that merges into a gaseous atmosphere. Saturn’s clouds form belts and zones similar to those on Jupiter but obscured by overlying haze. Storms and eddies, seen as red or white ovals occur in the clouds. Saturn has an extremely thin but wide system of rings that is about half a mile (1 km) thick but extends outward to about 260,000 miles (420,000 km) from the planet’s surface. The main rings comprise thousands of narrow ringlets, each made of icy rock lumps that range in size from tiny particles to chunks several yards across. The D, E, and G rings are very faint, the F ring is brighter, and the A, B, and C rings are bright enough to be seen from Earth with binoculars. In 2009, a huge dust ring was discovered 4 million miles (6 million km) beyond the main system.
Saturn has more than 60 known moons, some of which orbit inside the rings, and are thought to exert a gravitational influence on the shapes of the rings. Unusually, seven of the moons are co-orbital they share an orbit with another moon. Astronomers believe that such co-orbital moons may have originated from a single satellite that broke up.
