The fourth-largest satellite of Uranus, 1158 km in average diameter; also known as Uranus I. Ariel orbits Uranus in 2.52 days at a distance of 190 950 km, keeping the same face towards the planet. It was discovered in 1851 by W. Lassell. Ariel is an icy body, with a surface scored by giant steep-sided troughs, termed chasmata, between lightly cratered regions. The longest trough, Kachina Chasmata, is over 600 km long, and the largest crater, Yangoor, is 78 km wide. The erosion of some craters and the presence of smooth-floored material in the chasmata is evidence of volcanic or tectonic resurfacing by viscous ice flows.
Subjects: Astronomy and Astrophysics.