Uranus

Miranda shows the most interesting evidence for geologic activity and surface modification among Uranus' satellites. In addition to old cratered plains, canyons, scarps, lineaments, and valleys, the three coronae Arden, Elsinore, and Inverness exist on its surface; they are its most prominent surface features. They are large, lightly cratered regions of up to 186 mi (300 km) or more extent; Arden shows banded regions, while Elsinore and Inverness show numerous grooves and ridges. A cliff near Miranda's south pole may be as high as 12 mi (20 km). One plausible model for Miranda's evolution hypothesizes the following sequence of events. First, Miranda accreted from several smaller bodies near Uranus and nearly in its equatorial plane; impacts during accretion formed the old cratered plains. Some of the canyon systems were formed near the end of accretion. Next, a large body impacted Miranda, forming the Arden basin. Debris was scattered over and ejected from Miranda, and cryovolcanism flooded the basin, forming Arden Corona. Then the Inverness basin was flooded, forming Inverness Corona. The last main cryovolcanic activity formed Elsinore Corona. This left Miranda's surface early in its present state, with only a few more recent craters added since then.