An asteroid is one of tens of thousands of small, rocky, planet-like objects in orbit about the Sun.
Most asteroids lie between Mars and Jupiter, in a vast ring called the Asteroid Belt.
Every asteroid in the Asteroid Belt is in orbit about the Sun. About 100,000 asteroids may exist in the Asteroid Belt, but their total mass is only a few hundredths the mass of the Moon. The mass of all the asteroids combined is less than the mass of the smallest planet, Pluto. Even the largest asteroid is too small to have an atmosphere.