Accretion of Extraterrestrial Matter Throughout Earth's History : Springer : 9780306466892 : 0306466899 : 31 Oct 2001 : Every year Earth is bombarded with about 40,000 tons of extraterrestrial material. This includes microscopic cosmic dust particles shed by comets and asteroids in outer space, meteorites, as well as large comets and asteroids that have led to catastrophic events in the geologic past. Originally considered only a curiosity, extraterrestrial matter found on Earth provides the only samples we have from comets, asteroids and other planets. Only recently mankind has started to actively collect extraterrestrial matter in space (Apollo program, Stardust mission) rather than to wait for its delivery to Earth. Still, most of our knowledge of the origin and evolution of our solar system is based on careful studies of meteorites, cosmic dust, and traces of large impact events in the geologic record such as the mass extinction that terminated the Cretaceous Period an