Re: What is the ridged terrain on Ariel(Uranus Moon) , and how it have foemed?

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