(NASA, Jet Propulsion Laboratory, "Voyager, the Grandest Tour: The Mission to the Outer Planets," JPL 400-445, U.S. Government Printing Office, Washington, D.C., April 1991, p. 26.)
* Miranda may have been frozen in the midst of a geologic upheaval during which its body was almost literally turned inside out.
* Voyager 2's closest approach to Uranus on January 24, 1986, brought the spacecraft near Miranda. This was the closest satellite flyby of the encounter with Uranus. Miranda was the smallest of the five Uranian moons known before Voyager 2. It seems too small and cold to possess the diverse geologic features it has. Giant faults have sliced canyons as deep as 12 miles into the surface. Rolling plains that are heavily cratered about large patches of grooved and ridged terrain. These characteristics suggest Miranda may have undergone strong tidal heating in the past, possibly during the time when the small moon occupied a chaotic orbit around Uranus. Whatever forces shaped Miranda, they seem to have stopped.
* Planetary scientists have theorized that Miranda was frozen in the midst of a geologic process that most terrestrial (solid, Earth-like) bodies are thought to have undergone at an early age, a process in which the body almost literally turns inside out. Still other theories put forth that Miranda is the reaggregated sum of the parts of one or more moons that shattered in a collision with a comet.
* Most of the visible surface consists of relatively cratered terrain transected by fault scarps and fault-bounded valleys (graben). Some of the largest valleys are partly filled with younger, less heavily cratered deposits. Bright spots near the limb are chiefly the rims of small craters. Though the youngest features on Ariel, these brightly rimmed craters probably were formed over a long span of geological time. Even with a diameter of only about 1,200 kilometers (750 miles), Ariel has clearly experienced a great deal of geological activity in the past.
(The following is from "The Mission to the Outer Planets," NASA JPL 400-445, April 1991, p. 26.)
*Titania, the largest of Uranus' moons, shows long, deep fault lines.
* Umbriel is the darkest of Uranus' larger moons, reflecting only 21 percent of the sunlight it receives.
* Oberon's icy surface displays several large impact craters. A 13-mile-high peak protrudes at lower left.
(NASA, Jet Propulsion Laboratory, "Voyager at Uranus: 1986," JPL 400-268, U.S. Government Printing Office, Washington, D.C., July 1985, p. 5.)