Between the orbits of Mars and Jupiter is a swarm of thousands of space rocks ranging from 900 kilometers (560 miles) across to microscopic grains of dust. This region is known as the Main Asteroid Belt and it's where most of the asteroids in the Inner Solar System reside.

There are also countless thousands of comets in our solar system. These balls of ice and rock spend most of their time far from the center of the solar system in one of two reservoirs: the Kuiper Belt or the Oort Cloud.

The Kuiper Belt starts around the orbit of Neptune. It's actually kind of a wedge shape wrapped around itself into a donut with the thin edge facing in towards the sun.

The Oort Cloud is much farther away. It really is a cloud—a globular swarm of deep-frozen shards of matter left over from the formation of the sun and the planets.