Umbriel is the darkest satellite of Uranus. It is about the same size as Ariel and has about the same density. The surface appears to be old with large craters and does not change much from one location to another.

Near the top is a puzzling bright ring called the fluorescent cheerio. It is probably the floor of a crater.

NASA (Voyager 2) USGS

Earth

Mars

Jupiter

Saturn

Uranus

Neptune

Pluto

Eris