Effect of rotational disruption on the size-frequency distribution of the Main Belt asteroid population

The size distribution of small asteroids in the Main Belt is assumed to be determined by anequilibrium between the creation of new bodies out of the impact debris of larger asteroidsand the destruction of small asteroids by collisions with smaller projectiles. However, fora diameter less than 6 km, we find that YORP-induced rotational disruption significantlycontributes to the erosion even exceeding the effects of collisional fragmentation. Includingthis additional grinding mechanism in a collision evolution model for the asteroid belt, wegenerate size-frequency distributions from either an accretional or an 'Asteroids were born big'initial size-frequency distribution that are consistent with observations reported in Gladmanet al. Rotational disruption is a new mechanism that must be included in all future collisionalevolution models of asteroids.