Umbriel (moon)

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Umbriel is a moon of Uranus discovered in 1851 by William Lassell. Umbriel's surface is the darkest of the Uranian moons, and it is also the least geologically active. It is mostly composed of water ice, with the balance made up of silicate rock and methane ice. Most of its methane ice is on its surface.

Umbriel is the 'dusky melancholy sprite' in Alexander Pope's The Rape of the Lock. The name suggests the Latin umbra, shadow.

• Diameter: 1190 km
• Surface Area: 4,300,000 km²
• Orbital radius: 266,000 km
• Rotation period: 4.14 days
• Orbital period: 4.14 days