Of the many moons around Saturn, Mimas is the closest to the planet. First discovered in 1789 by the British astronomer William Herschel, it lies about 186,000 kilometers (115,000 miles) from Saturn. This distance is only half the distance between the Earth and the Moon. Mimas needs only 22.5 hours to complete its orbit around Saturn.

Mimas can be seen at the bottom of this image taken by the Cassini spacecraft in 2005. Behind it, Saturn's northern latitudes glow a cool blue and shadows from its rings cast long, dark streaks through the atmosphere.

Image description:

Saturn's surface takes up most of this image, with thin, dark lines arcing down and to the right above the periwinkle-colored atmosphere. At the bottom, just left of center, the moon Mimas appears as a gray, slightly dimpled circle.

Credit: NASA/JPL-Caltech/Institute for Space Science