In a way, asteroids, comets and meteorites are different words for basically the same thing – smallish space rocks. The main distinction is where they form in the solar system. Asteroids are usually born in the inner solar system – from Jupiter inwards – while comets form further out. Thanks to the much colder conditions on the fringes of the solar system, comets contain more water ice and far more carbon than asteroids. Meteorites, meanwhile, are the fragments that survive the fall to Earth, and can be the remains of either comets or asteroids.