Between Mars and Jupiter in our solar system, there is a massive ring of asteroids that orbit the Sun. These make up what is known as the asteroid belt, and they vary in size, from really small rocks just inches in diameter, to the largest known asteroid, Ceres, which is over 600 miles across.
But how did they all get there, and why are they all in one place? There are some theories suggesting that the asteroid belt's contents once made up a planet, and that some kind of destruction of that planet from a sudden impact may have destroyed it, causing it to crumble into a million pieces.
But how likely is that? - Considering what we know about our solar system, maybe not so much, but it's definitely worth a thought. On the other hand, the planets closest to the Sun are solid, while the planets furthest from the Sun are gas, and that asteroid belt separates those two distinct types of planets.
So it's possible that gravity could have played a role here, and that there was just too much interference for all of the little rocks to combine into a full-sized planet over time.