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7.31 Uranus' Miranda

Of Uranus' several modest-sized satellites, the inner moon Miranda is most noteworthy, despite its smaller size. Miranda is only 470 kilometers across, or about one-seventh the size of Earth’s Moon. Voyager 2 was forced to swing close by Miranda on its way out of the Uranian system toward Neptune. Although scientists expected it to be geologically inert because of its small size, what they found was the most fascinating satellite in the system. Miranda was discovered in 1948 by planetary scientist Gerard Kuiper; the first new satellite of Uranus to be identified in a century. It was named after a character in Shakespeare's "The Tempest," in accordance with previous naming of moons of Uranus.


Miranda, a moon of Uranus. Click here for original source URL.

The icy surface is heavily cratered, like that of other Uranian satellites. However, Miranda also has unique swaths of younger, ridged and fractured terrain. These features are reminiscent of the icy swaths on Jupiter's much larger satellite, Ganymede. One cliff face is among the highest in the Solar System, rising as much as 5 kilometers (16,000 feet) in a smooth, 45° angled slope. One canyon is 20 kilometers (12 miles) deep. 

The question of Miranda’s complex past puzzles researchers.  How did Miranda become so heavily fractured? Like Jupiter's satellite, Io, tidal forces may have heated the interior, leading to tectonic activity that caused the fractures. Or perhaps one or more violent impacts with interplanetary bodies broke Miranda apart, exposing interior layers. The jumbled pieces then congregated into the jagged satellite. Another hypothesis involves incomplete differentiation of the satellite: the idea that less dense material rose to the surface in some areas, creating patches of younger ice. Whatever the explanation, we will probably have to wait until another mission is sent to the outer Solar System for more clues to Miranda’s mysterious history.