Oberon (moon) at the core–mantle boundary. The eutectic temperature of this mixture is 176 K. If the temperature dropped below this value the ocean would have frozen by now. Freezing of the water would have led to expansion of the interior, which may have also contributed to the formation of canyon-like graben. Still, present knowledge of the evolution of Oberon is very limited. So far the only close-up images of Oberon have been from the "Voyager 2" probe, which photographed the moon during its flyby of Uranus in January 1986. Since the closest approach of "Voyager 2" to Oberon was 470,600 km,
Oberon (moon) largest craters, Hamlet, Othello and Macbeth, have floors made of a very dark material deposited after their formation. A peak with a height of about 11 km was observed in some "Voyager" images near the south-eastern limb of Oberon, which may be the central peak of a large impact basin with a diameter of about 375 km. Oberon's surface is intersected by a system of canyons, which, however, are less widespread than those found on Titania. The canyons' sides are probably scarps produced by normal faults which can be either old or fresh: the latter transect the bright deposits of