Saturn is the second-largest planet in the Solar System and, like Jupiter, is a gas giant made primarily of hydrogen and helium. It is best known for its spectacular ring system, the most extensive and visible of any planet. The rings are made up of countless particles of ice and rock that range in size from tiny grains to chunks several metres across, organized into thousands of distinct ringlets separated by gaps.

Saturn is the least dense planet in the Solar System. Its average density is lower than that of water, which means that, given a large enough ocean, Saturn would float. The planet is also notable for its strong winds, among the fastest in the Solar System, and for a long-lived hexagonal cloud pattern that surrounds its north pole.

Saturn has dozens of confirmed moons. The largest, Titan, is bigger than the planet Mercury and is the only moon in the Solar System with a substantial atmosphere, a thick haze of nitrogen and methane. Titan has lakes and rivers of liquid methane and ethane on its surface, making it one of the most Earth-like environments known, despite its frigid temperatures. Another moon, Enceladus, vents plumes of water vapour from a subsurface ocean.
