Asteroids are relatively small (compared to moons and planets), rocky objects in our solar system. They range in size from a few feet across to behemoths like Ceries, which is 580 miles (933 kilometers) in diameter. The majority of asteroids can be found in the Asteroid Belt, a band of rocks orbiting between Mars and Jupiter. The origin of asteroids remains the subject of scientific study. Astronomers today think that most asteroids are planetesimals that never quite combined with other bodies to form planets. Some asteroids, on the other hand, may be the shattered remains of planets or protoplanets that suffered huge collisions and broke into pieces. Asteroids range in composition from “rubble piles” that are loose collections of rock held together by gravity (e.g., the Mathilde asteroid) to solid rock (Eros) to asteroids with high metallic content (Kleopatra). Some asteroids are so large that they exert gravitation and have tiny moons orbiting them.