The distribution of heavy elements is anomalously low in the asteroid main belt region compared with elsewhere in the solar system .
Observational surveys also indicate a deficit in the number of small ( \la 50 km size ) asteroids that is two orders of magnitude lower than what is expected from the single power-law distribution that results from a collisional coagulation and fragmentation equilibrium .
Here , we consider the possibility that a major fraction of the original asteroid population may have been cleared out by Jupiter ’ s secular resonance , as it swept through the main asteroid belt during the depletion of the solar nebula .
This effect leads to the excitation of the asteroids ’ orbital eccentricities .
Concurrently , hydrodynamic drag and planet-disk tidal interaction effectively damp the eccentricities of sub-100 km-size and of super-lunar-size planetesimals , respectively .
These combined effects lead to the asteroids ’ orbital decay and clearing from the present-day main belt region ( \sim 2.1 - 3.3 AU ) .
Eccentricity damping for the intermediate-size ( 50 to several hundreds of kilometers ) planetesimals is less efficient than for small or large planetesimals .
These objects therefore preferentially remain as main belt asteroids near their birthplaces , with modest asymptotic eccentricities .
The smaller asteroids are the fragments of subsequent disruptive collisions at later times as suggested by the present-day asteroid families .
This scenario provides a natural explanation for both the observed low surface density and the size distribution of asteroids in the main belt , without the need to invoke special planetesimal formation mechanisms .
It also offers an explanation for the confined spatial extent of the terrestrial planet building blocks without the requirement of extensive migration of Jupiter , which is required in the grand-tack scenario .