Asteroids orbit the sun and are smaller than planets but larger than meteoroids. They are mostly rocky bodies without atmospheres. Meteorites originate from asteroids and comets and survive atmospheric entry and impact, becoming meteors as they heat up in the atmosphere. The largest group of asteroids is in the asteroid belt between Mars and Jupiter, which formed from material that failed to form a planet due to Jupiter's gravitational influence. Meteorites can be classified based on their composition as chondrites, achondrites, iron, or stony-iron meteorites.