This image of the asteroid Ida was captured by the Galileo spacecraft while on its way to Jupiter. The image shows many craters on the asteroid's surface. Ida is one of thousands of asteroids in the asteroid belt that is located between the orbits of Mars and Jupiter. It has an average diameter of 31.4 kilometers (19.5 miles). The material in the asteroid belt is believed to be a failed planet. The strong gravitational pull of Jupiter may have prevented a planet from forming from this debris.