Mimas

Mimas, also designated Saturn I, is a natural satellite of Saturn that has the second largest crater on any moons in the Solar System, named the Herschel crater. The Herschel crater measures 139 kilometres (86 miles) across, about one-third of Mimas's mean diameter (396.4 kilometres or 246.3 miles), and is believed to be formed from an extremely energetic impact event. The crater's name is derived from the discoverer of Mimas, William Herschel, in 1789. 
Mimas is the smallest astronomical body known to be roughly rounded in shape due to its own gravity. Mimas's low density, 1.15 g/cm3, indicates that it is composed mostly of water ice with only a small amount of rock. The moon's presence has created one of the largest 'gaps' in Saturn's ring, named the Cassini Division, due to orbital resonance destabilizing the particles' orbit there.
Category:Moons
Category:Saturnian Moons
Category:Objects In Hydrostatic Equilibrium
Category:Objects with Transient Atmospheres
Category:Outer Solar System Object
Category:Prograde Satellite
Category:Named Objects
Category:Named Moons
Category:Numbered Objects
Category:Numbered Moons
Category:Major Moon of Saturn
Category:Objects Visited by Spacecraft