Asteroid+Belt

The asteroid belt is a region between the inner and outer planets. The area is home to many asteroids, thus its name, and many minor planets (objects that are bigger than meteoriods  but smaller than actual planets).

It is believed that during the first million years of the Solar System, a process of collisions caused small particles to clup together and slowly get bigger and bigger in size. Once the clumps reached a good size hey could draw in other bodies through gravitational attraction. This gravitational attraction led to the formation of the rocky planets and the gas giants. Planetesimals within the region which would become the asteroid belt were too strongly perturbed by gravity to form a planet. Instead they continued to orbit the Sun as before, while occasionally colliding.

Over the years the asteroid belt has undergone much change since its formation. This includes surface melting, internal heating, space weathering due to radiation , and bombardment by micrometeorites. Our current asteroid belt is is only a small fraction of the original. Computer simulations suggest that the first asteroid belt had a mass identical to that of Earth. Mainly because of gravity, most of the material was expelled from the belt in the first million years following its formation. The belt now contains only 0.1% of its original mass.

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