Four icy satellites of Uranus

Four icy satellites of Uranus

. Uranus has four large ice-covered moons that display impact craters, bright rays of ejected material, smooth regions and large rifts or grooves. They range in size from 580 thousand meters in radius, for Ariel, to a radius of 805 thousand meters for Titania. Numerous valleys and faults cross the terrain of Ariel (top left). The darkest large moon is Umbriel (top right), which reflects only 16 percent of the sunlight striking its surface. Its heavily-cratered surface resembles the lunar highlands, but lacks the numerous bright-ray craters and evidence for geological activity seen on the other large satellites. Titania (lower left) retains the numerous scars of impacts, with bright icy ejected material, as well as a trench-like feature that suggests tectonic activity (right edge). The icy surface of Oberon (lower right) exhibits several large impact craters surrounded by bright rays. One of them has a bright central peak and a floor that is partially covered with very dark, possibly carbon rich, material that may have erupted onto the crater floor sometime after the crater formed. These images were taken from the Voyager 2 spacecraft on 24 January 1986. (Courtesy of NASA and JPL.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University