Polarised light micrograph of Krymka meteorite. Meteorites are thought to be broken fragments formed by collisions between asteroids, orbiting the Sun in a belt between Mars & Jupiter. The fragments resulting from the collisions are deflected into orbits that cross the path of the Earth. Meteorites vary in size from fine dust particles to bodies several miles in diameter that have made large craters on impact with the Earth, Moon or Mars. There are 3 main types of meteorites: stony, iron and stony-iron. Stony-iron (rock-based) meteorites are the most common.