Titania's Trenches . ... Credit Copyright: The Voyager Project , NASA Explanation: British astronomer Sir William Herschel discovered Titania and Oberon in January of 1787. ... Above is Voyager's highest resolution picture of Titania , Uranus' largest moon. The picture is a composite of two images recorded from a distance of 229,000 miles. The icy, rocky world is seen to be covered with impact craters. ... Titania itself is 1,000 miles in diameter. ... NASA Official: Jay Norris. ...