Uranus' Dark Moon

Umbriel is the fourth largest satellite orbiting Uranus. Unlike the other moons orbiting Uranus, this moon is strangely dark. In fact, it reflects only about half the light of the other moons. Given the distance of Uranus from Earth, Voyager 2 is the only spacecraft has visited this planet. Further, Umbriel has two bright white spots on an otherwise dark surface. Paul Helfenstein, Peter C.Thomas and Joseph Veverka, writing for Nature in 1989, have theorized that the bright spots on Umbriel are recent impact craters. There is much left to learn about this satellite and its mysterious past.

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