The Main Asteroid Belt

The Asteroid Belt is the space between Mars and Jupiter. It contains irregularly shaped chunks of debris called asteroids.

The main asteroid belt extends from 255 to 600 million km (2.15 to 3.3 astronomical units) from the Sun and may contain over a million objects bigger than 1 km across. The largest objects are Ceres (1,003 km), Pallas (608 km), and Vesta (538 km).

More than 100,000 asteroids lie in a belt between Mars and Jupiter. These asteroids lie in a location in the solar system where there seems to be a jump in the spacing between the planets.

Scientists believe the asteroids are the pieces of a planet that never formed. One possible theory is the ongoing gravitational tug-of-war between Jupiter and Mars has prevented the pieces from bonding together, hence, this planet was never created. Others believe they are the reains of an early planet, which broke up early in the solar system.

Several thousand of the largest asteroids in this belt have been given names. These Space Asteroids are made of rock and metal, mostly nickel and iron.

The first flybys of asteroids were performed in 1991 and 1993 by NASA's Galileo spacecraft and in 1996 by the Near Earth Asteroid Rendezvous (NEAR) spacecraft.

In the 1980's, the Soviet Union was planning to send a probe to Vesta. No information available on its status.