Uranus Moon Miranda
Photograph courtesy NASA/STI (Science and Technical Information) Program
The unusual surface of Miranda, one of Uranus's 27 known moons, is a jumble of haphazard features: huge fault canyons, terraced layers, and a mixture of young and old surfaces. Since the mixing of ancient and recent surfaces is rare in planetary geology, scientists have postulated two explanations for the different ages of the numerous valleys and cliffs on Miranda. One theory is that Miranda could have shattered as many as five times and was then reassembled. Another hypothesis is that upwells of partly melted ice forced new surfaces to emerge.