The number of objects in the original asteroid belt

Using the limited collisional evolution of Ceres and Vesta as constraints for the number of objects in the asteroid belt it is found that a moderate mass depletion by a factor of 3.6 occurred after the end of the accretion period. To model the angular momentum evolution a “particle-in-a-box” method is used which takes into account the size distribution of the actual belt and the loss of angular momentum by ejecta escaping preferentially in the prograde direction. It also provides a value of 0.26 for the fraction of leftover impact energy available for further mechanical work after a collision, which is higher than the values used by other authors for simulations. In a belt with these properties the survival during the Solar System age for objects with the dimensions of Vesta is granted, but for asteroids ≈ 300 km in diameter the survival probability is a strong function of the region where the object moves.