Perspectives on the comet-asteroid-meteorite link

We discuss the possibility that CI and CM carbonaceous chondrites are fragm ents of extinct cometary nuclei. Theoretical and observational work suggest s that comets evolve into asteroids, and several extinct cometary nuclei ar e now suspected to he among the near Earth object population. This populati on is the most likely source of meteorites and consequently, we may expect that some meteorites are from extinct comets in this population. The minera logy and chemistry of CI and CM chondrites is consistent with the view that they originate from asteroidal objects of carbonaceous spectral classes, a nd these objects in turn may have a cometary origin. We do not suggest that CI or CM chondrites are directly delivered by active comets during perihel ion passage or that these chondrites come from cometary debris in meteor st reams. Instead, we summarize arguments suggesting that CI and CM chondrites represent fragments of cometary nuclei which evolved into near Earth aster oids after losing their volatiles.