Hyperion is a moon of Saturn discovered by William Cranch Bond, George Phillips Bond and William Lassell in 1848. It is named after Hyperion, a Titan in Greek mythology. It has a low density indicating that it is composed largely of water ice with a small amount of rock. It is covered by at least a thin layer of dark material. Hyperion is one of the largest highly irregular bodies in the Solar System. The largest crater on Hyperion is approximately 120 km in diameter.