The origin of meteorites as small bodies. II. The model

Abstract

A Monte Carlo method has been used to follow the fate of meteoritic fragments ejected into the inner Solar , on various asteroidal, lunar, and cometary models of their origin. The method is based on a theory of Opik. It takes into account major perturbations caused by close approaches to the planets and destruction by further collisions with asteroids The distributions of bombardment ages and of final orbital parameters are given in a form suitable for comparison with observation. Ages as short as those observed for chondrites can be obtained for an asteroidal origin, but only if the destructive cross-section of the asteroids is taken to be 5-20 times that of Jupiter. The age distribution for chondrites depends markedly on origin, very short ages being common for a lunar origin and almost non-existent for an asteroidal one. However, if most meteorites were made in a few great events, the data will not show a clear distinction. The orbital parameters are similar but not identical for lunar and asteroidal origin. The best possible test would be to have the orbital parameters of a meteorite of very short bombardment age, such as the chondrite Farmington. The bombardment ages for iron meteorites are consistent with an asteroidal origin.