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Planet Uranus

Mysterious Umbriel

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Planet Uranus - Mysterious Umbriel

Umbriel is an enigma. It has a surface albedo of only 10-15%, while the rest of the Uranian satellites found inside and outside Umbriel's orbit are much brighter. The process by which Umbriel's ancient cratered surface was darkened, leaving only a few bright icy white rings, remains a mystery.