Ida was the 243rd asteroid discovered
Facts on Ida
How fast does Ida travel?
Picture taken by Galileo
More about Ida
Ida is a heavily cratered, irregularly shaped asteroid in the main asteroid belt between Mars and Jupiter -- the 243rd asteroid to be discovered since the first one was found at the beginning of the 19th century. Ida is placed by scientists in the S class (stony or stony iron meteorites). It is a member of the Koronis family, which scientists believe was created when a larger body perhaps 200 to 300 kilometers (120 to 180 miles) in diameter was smashed relatively recently -- at least considerably after the solar system formed some 4.5 billion years ago.
On August 28, 1993 Galileo came within 2,400 kilometers (1,500 miles) of 243 Ida, the second asteroid ever encountered by a spacecraft. They passed each other at a relative velocity of 12.4 km/sec (28,000 mph). At the time of the encounter, Ida and Galileo were 441 million kilometers (274 million miles) from the Sun.
Ida is about 56 x 24 x 21 kilometers (35 x 15 x 13 miles) in size, more than twice as large asGaspra. It has a period of rotation of 4 hours, 38 minutes. Its density has been estimated to be between 2.2 and 2.9 grams per cubic centimeter. Ida's age is somewhat baffling. Its surface is heavily cratered suggesting that it has existed in its present form for at least a billion years and perhaps much longer. It is also considerably older than estimates for the Koronis breakup.