Efficient delivery of meteorites to the Earth from a wide range of asteroid parent bodies

Almost all meteorites come from asteroids, but identifying their specific p arent bodies, and modelling their transport to the Earth, has proved to be difficult(1,2). The usual model(1,3,4) of delivery through orbital resonanc es with the major planets(5,6) has recently been shown(7-10) to deplete the supply of meteorites much too rapidly to explain either the observed flux at the Earth, or the length of time the meteorites have spent in space (as measured by cosmic-ray exposure ages). Independently, it has been found tha t a force arising from anisotropically emitted thermal radiation from aster oidal fragments (the 'Yarkovsky effect') influences the fragments' orbits i n important ways(11-14). Here we report the results of a detailed model for the transport of meteorites to the Earth, which includes the Yarkovsky eff ect and collisional evolution of the asteroidal fragments. We rnd that the Yarkovsky effect significantly increases the efficiency of the delivery of meteorites to the Earth, while at the same time allowing a much wider range of asteroids to contribute to the flux of meteorites. Our model also repro duces the observed distribution(15,16) of cosmic-ray exposure ages of stony meteorites.