Description

The Earth is bombarded constantly by material from space. Evidence of this bombardment comes both from craters that may form prominent features in the landscape, and samples of the impactors curated as meteorites. Since the impact of extraterrestrial material on Earth has the potential to be of more than local significance, and can lead to effects traceable in both the geological and biological record, it is important to obtain an accurate picture of the extent of bombardment. Several techniques have been used to derive estimates for the flux of extraterrestrial material to the Earth, both now and throughout the geological record. The methods used to assess meteorite fluxes and impact effects are diverse and involve scientists from different communities (geologists, geochemists, biologists and astronomers).The volume commences with description of the meteorite flux with time, covering both small bodies (including strewn fields and the problem of 'pairing' of meteorites) and large bodies capable of producing craters and cryptoexplosion features. The discussion includes the different ways in which the flux has been determined (from observational astronomy, meteorite collection statistics and the oretical calculations). Following on this comes the documentation of impacts in the geological record and their effects on the environment, focusing specifically on the Cretaceous-Tertiary (K/T) boundary mass extinction event. Although the geophysical and geochemical evidence for a large impact at the end of the Cretaceous period is quite clear, the possible environmental consequences of an impact are still a matter of active debate, and the fossil record is by no means an unambiguous record of the mass extinction so frequently reported. Principle Authors: M. M. Grady, Natural History Museum, UK.E. M. Shoemaker, Lowell Observatory, USA.M. E. Bailey, Armagh Observatory, UK.W. M. Napier, Armagh Observatory, UK.D. W. Hughes, University of Sheffield, UK.P. A. Bland, Western Australian Museum, Australia.A. W. R. Bevan, Western Australian Museum of Natural Science, Australia.A. J. T. Jull, University of Arizona, USA.M. Zolensky, NASA Johnson Space Center, USA.R. A. F Grieve, Geological Survey of Canada, Canada.C. Koeberl, University of Vienna, Austria.A. R. Hildebrand, Geological Survey of Canada, Canada.P. K. H. Maguire, University of Leicester, UK.J. G. Spray, University of New Brunswick, Canada.I. Gilmour, The Open University, UK.N. MacLeod, The Natural History Museum, UK.A. C. Milner, The Natural History Museum, UK.A. Hallam, University of Birmingham, UK