Oberon

Oberon is Uranus's outermost large moon. It orbits Uranus at an average distance of 362,000 miles (583,000 km), with an orbital period of 13.46 days. Oberon was discovered in 1787 by William Herschel.

Oberon is 945 miles (1520 km) in diameter, making it the second-largest Uranian moon (after Titania). So far the only close-up images of Oberon's surface are from the Voyager 2 spacecraft, which photographed the moon during its 1986 Uranus flyby. Voyager 2's images show an old, icy, and heavily cratered surface, with little evidence of internal activity. Some unknown dark material covers the floors of many craters, and a few large faults can be seen across the southern hemisphere. Oberon is composed of roughly 50% water ice, 30% silicate rock, and 20% methane/carbon/nitrogen compounds.