Umbriel as seen by Voyager 2 in 1986
|Discovered by||William Lassell|
|Discovery date||October 24, 1851|
|266 000 km|
|Inclination||0.128° (to Uranus's equator)|
|584.7 ± 2.8 km (0.092 Earths)|
|4 296 000 km2 (0.008 Earths)|
|Volume||837 300 000 km3 (0.0008 Earths)|
|Mass||1.172 ± 0.135 × 1021 kg (2 × 10−4 Earths)|
|1.39 ± 0.16 g/cm3|
|0.2 m/s2 (~ 0.023 g)|
|14.5 (V-band, opposition)|
So far the only close-up images of Umbriel are from the Voyager 2 probe, which made observations of the moon during its Uranus flyby in January, 1986. During the flyby the southern hemisphere of the moon was pointed towards the Sun so only it was studied.
Umbriel's surface is the darkest of the Uranian moons, and reflects only about half as much light as Ariel, Uranus' brightest moon. It has far more and bigger craters than do Ariel and Titania and is also the least geologically active. It is mostly made of water ice, with the balance made up of silicate rock, and other ices such as methane. Methane can break down and form reddish-black organic compounds such as tholins when bombarded by high-energy particles. Near-IR spectra of Ariel and Umbriel clearly show that water ice dominates the spectra of these objects.
Craters on Umbriel are named after many different demons from various mythologies.
|Malingee||Malingee (Australian Aboriginal mythology)|
|Minepa||Minepa (Makua people of Mozambique)|
|Wokolo||Wokolo (Bambara people of West Africa)|
|Wunda||Wunda (Australian Aboriginal mythology)|
Images for kids
Umbriel (moon) Facts for Kids. Kiddle Encyclopedia.