Leda is Jupiter's ninth and smallest moon. Leda is 9.9 miles (16 km) in diameter and orbits at an average of 6,900,000 miles (11,094,000 km) from Jupiter. Leda has a mass of 5.68 x 10 15 kg. It orbits Jupiter in 238.72 (Earth) days. Very little is known about Leda. Leda was discovered by Charles Kowal in 1974.
Leda (lee'-də, ; Greek Λήδα), or Jupiter XIII, is a prograde irregular satellite of Jupiter that was discovered by Charles T. Kowal at the Mount Palomar Observatory on September 14, 1974, right after three nights' worth of photographic plates had been taken (September 11 through 13; Leda appears on all of them). It is named after Leda, the queen of Sparta who was the mother of Castor, Polydeuces, Clytemnestra and Helen of Troy (Zeus, in the form of a swan, was the father).