Dark moon of UranusThe quietest face of Uranus
Umbriel
Umbriel is the darkest major moon of Uranus, an ancient cratered world with one enigmatic bright ring.
- Host
- Uranus
- Type
- Dark icy moon
- Mean diameter
- 1,169 km
- Mean orbital radius
- 266,000 km
- Orbital period
- 4.14 days
- Surface gravity
- 0.20 m/s²
- Key feature
- Wunda bright ring
- Discovered
- 1851 · William Lassell
Umbriel up close
NASA imagery
An ancient dark surface
Umbriel's low albedo makes it look nearly featureless from a distance. At higher resolution, Voyager 2 found a densely cratered landscape with few broad tectonic or volcanic features.
The darkness may come from radiation-processed material mixed into the surface. Beneath a layer of dark dust or frost, water ice likely remains abundant.
Wunda and the missing history
A bright ring-shaped feature called Wunda stands out near Umbriel's equator. It may be a fresh impact crater or an area where frost has been exposed by geological activity.
Most of Umbriel remains unobserved at high resolution. Its muted surface could preserve evidence of ancient processes erased elsewhere in the Uranian system.
Worth knowing
Umbriel is named after a melancholy sprite in Alexander Pope's The Rape of the Lock.
It is the darkest of Uranus's five largest moons.
Voyager 2 saw only one hemisphere during its 1986 flyby.
Watch and explore
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Umbriel's Close Encounter Cosmic Pulse
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Research & further reading
Mission imagery and measurements are interpreted alongside orbital data. Follow the source links for the current NASA overview and precise satellite parameters.