Of the five moons of Uranus, the only one to really stand out would be Miranda. One look at the moon suggests that some kind of cataclysmic event must have taken place in its past - huge fault canyons and ridges run across its surface. However, newer theories have replaced the idea that Miranda was shattered several times and instead suggest that somehow internal heating has caused lighter materials to rise up in various locations to the surface. Internal heating in smaller objects (Miranda is about 470km wide) is no longer an unexpected thing in the outer solar system. If it is ever confirmed that Miranda does in fact experience internal heating it will join Enceladus, Io and Europa (and possibly others) in this whole new class of body to be explored in the Solar System.