Exploring Miranda. Artist's impression of atronauts exploring`a cliff on the Uranian moon Miranda. Miranda is a small moon - only 470km in diameter - and lies on average 130,000km away from Uranus. Its rocky surface is scarred by mysterious craters, grooves and swirling track-marks of unknown origin. One of its most bizarre features is a sheer cliff about 20km tall - a colossal structure on a world that is less than a twentieth the diameter of Earth.