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Ariel ("AIR ee el") is the twelfth of Uranus's known satellites:
orbit: 190,930 km from Uranus
diameter: 1158 km
mass: 1.27e21 kg
Ariel is a mischievous airy spirit in Shakespeare's The Tempest.
Discovered by Lassell in 1851.
Ariel and Titania appear quite similar though Titania is 35% larger. All of Uranus' large moons are a mixture of about 40-50% water ice with the rest rock, a somewhat larger fraction of rock than Saturn's large moons such as Rhea.
Ariel's
surface is a mixture of cratered terrain and systems of
interconnected valleys hundreds of kilometers long (left,
above) and more than 10 km deep. This is similar to, but much larger
and more extensive than the situation on Titania. Some of the craters
appear to be half-submerged. Ariel's surface is clearly relatively
young
(though older than some such as Enceladus);
obviously some sort of resurfacing processes have been at work. Some
ridges in the middle of the valleys are interpreted as upwellings of
ice.
Ariel
may have been hot inside long ago, but it's cold now. Perhaps the
valleys are cracks which formed when Ariel froze.
... Uranus ... Miranda
... Ariel ... Umbriel ... 
