Uranus, the seventh planet from the Sun, has twenty-seven moons. Rather than being named for Greek or Roman mythology, the moons all take their names from the works of Shakespeare and Alexander Pope. Miranda is one of the most interesting of the five larger Uranian moons. All of Uranus’ large moons are composed of roughly equal amounts of water, ice and silicate rock – Miranda is no exception. Unlike the other moons, though, Miranda’s orbit is slightly inclined. Of the five main moons, it is the smallest and closest to the planet.
Though only a seventh of the size of Earth’s moon at approximately 500 km (310 miles) in diameter, Miranda is home to a great deal of tectonic activity. In addition, it has one of the most varied and bizarre landscapes in all of the solar system. The surface of Miranda looks like it is composed of numerous patchwork pieces. The pieces do not even appear to fit together correctly.
Miranda features three coronae, which are lightly cratered areas that form ridges and valleys. They contrast sharply with the more heavily cratered regions that are assumed to be older. The coronae contribute to the mismatched appearance of Miranda’s surface. The moon also has huge fault canyons that are twelve times deeper than the Grand Canyon.
Scientists do not agree about the processes involved in the formation of Miranda. One theory is that the satellite was created when a larger body was smashed apart. Gravity then caused some of the pieces to come back together, but in no particular way, making it literally a patchwork of other pieces. A more likely theory is that the coronae were caused by rocky or metallic meteorites. The impacts partially melted the ice below the surface, which caused water to rise and refreeze, thus changing the landscape.
Miranda is a fairly bright moon. It is nearly as bright as Ariel, which is the brightest of Uranus’ moons. None of the moons, though, reflect more than a third of the light from the Sun that reaches them. This phenomenon implies that their surfaces have actually been darkened by carbonaceous material. Miranda appears substantially brighter when the observer is directly between it and the Sun. The dramatic changes, depending upon the angle at which the moon is viewed, mean that it is porous. Eons of micrometeorites hitting Miranda and essentially tilling the soil may have caused it.
Gerard P. Kuiper discovered Miranda in telescopic photos on February 16, 1948, at the McDonald Observatory in western Texas. It was the last of the Uranian moons discovered prior to the Voyager 2’s visit in 1986, when the other twenty-two moons were identified. Miranda is named for the daughter of Prospero in Shakespeare’s “The Tempest.” Miranda is the only female character in the entire play.