Uranus from Ariel. Artwork of the surface of Ariel, with Uranus and its rings and moons seen in the sky. Ariel is one of Uranus's five major satellites, with a diameter of 1200km. Much of the surface is densely pitted with craters, 5-10km across, with numerous valleys and fault scarps criss-crossing the terrain. Extensive faulting has occurred as a result of expansion and stretching of Ariel's crust. The largest fault valleys have been partly filled with deposits that are younger and less heavily cratered. Narrow, sinuous (winding) scarps and valleys have been formed later in these young deposits, either by faulting or fluid flow.