243 Ida is a member of the Koronis family of asteroids. Iit was discovered by Johann Palisa in 1884 and named after the mountain
on Crete where Zeus spent his childhood. On August 28, 1993, it became the
second asteroid, after Gaspra, to be encountered
by a spacecraft when Galileo flew past it
at a distance of 2,400 km and with a relative velocity of 12.4 km/s. The
highlight of the flyby was the discovery (made in February 1994 when images
stored on the spacecraft's tape recorder were finally transmitted to Earth)
that Ida has a satellite, subsequently christened Dactyl.
Ida's age is a puzzle. Its surface is heavily cratered suggesting that it
has existed in its present form for at least a billion years, which predates
estimates for the Koronis breakup.
||56 × 24 × 21 km
ASTEROIDS, CENTAURS, AND KUIPER BELT OBJECTS