Asteroid Belt The Asteroid belt is an orbit of asteroids between the orbits of Mars and Jupiter. It is in this area where the most number of asteroids can be found. The asteroids though are not highly concentrated, and are not very close together. Not many of the asteroids exceed 100 km, only about 220 out of the thousands that are there. The largest asteroid there is the 1000 km in diameter dwarf planet, Ceres. Asteroid collisions occur very frequently. At high speeds the collisions can splinter the asteroids and create new ones, but at slow speeds, the asteroids can fuse together to form one.