Also, the range of sizes of meteoritic crystals suggests than many of them are on the large-side which also points to a slow cooling process like the kind you would find inside a rather large parent body. We know that, when the solar system was young, there were many such 'planetessimals' in the solar system because we can see impact craters on distant moons that require very large bodies to produce them. We think that some may have been trapped in the region of the asteroid belt, and then suffered collisions.
Differentiation requires a strong, local gravitational field.
Slow cooling and large crystal patterns also require a large body. This is why the evidence points to the collision of a few large bodies, rather to material that never could get assembled into a planet, as the origin of the asteroid belt. Dr. Sten Odenwald Return to Ask the Astronomer .