Oberon

Voyager 2 image of Uranus' satellite Oberon from 663,000 km. The dark spot to the right of center is the 206 km diameter crater Hamlet. Oberon, the most distant major satellite from Uranus has a diameter of 1523 km. Oberon has an old, heavily cratered surface with little evidence of internal activity other than some unknown dark material apparently covering the floors of many craters.