The asteroid that has its own moon is 243 Ida. It is a small, irregularly shaped asteroid about 32 kilometers in diameter, located in the main asteroid belt between Mars and Jupiter. Ida is notable for being the first asteroid to be visited by a spacecraft, the Galileo mission in 1993, which discovered its small moon, Dactyl. Dactyl is about 1.6 kilometers in diameter and orbits Ida at a distance of about 100 kilometers.