|MadSci Network: Astronomy|
Ariel is one of Uranus' many moons. It has a diameter of 1158 km, is 191,400 km from Uranus' centre, and is brighter (higher albedo) than Umbriel and Titania Its surface is more variegated than Umbriel or Titania, and shows polygonal plains (mesas) criss-crossed by deep canyons and fissures bounded by faultlines. These are believed to be evidence of widespread geological activity carried down into more recent times than other moons. The canyon floors are centrally filled with icy volcanic material which shows greater viscosity than comparable formations in the Saturnian moons. Crater densities show that tectonism and volcanism have been active on Ariel for a long time. Its surface is icier than other Uranian satellites. The heating effects are believed to be too extensive to be simply radiogenic in origin, and so tidal effects are postulated (as on Jupiter's Europa). Resonant couplings between the orbits of Titania and Ariel in the past are believed to have led to tidal flexion and heating, causing tectonic geological activity, faulting and ice volcanism. The ice would be more viscous than at Saturn becaue of the generally colder environment some 1500 million kilometres further from the Sun than Saturn. Ref: The New Solar System 4th Edition 1999, Beatty, Chaikin and Peterson
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