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1 Department of Mineralogy, Natural History Museum, Cromwell Road, London SW7 5BD, UK
2 Honorary Fellow, Liverpool University: Honorary Associate, Western Australian Museum, Perth, UK
3 Department of Earth Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA, UK
The subject of this Special Publication is the flux with time of meteorites and their effects on this planet. Determining the flux of impacting objects from space to the Earth is difficult and estimates have in the last two decades achieved improved validity as a result of extensive researches on optimum fields of preservation such as Antarctica and desert areas such as the Nullarbor Plain, Australia and the Sahara. The impactors to the Earth come from the asteroid belt, the Moon and almost certainly Mars (the last two spalled off by impacts on those bodies); and also it is believed the cometary clouds of the outer Solar System. In recent years it has been recognized that large impactors from space, though representing rare events in the four thousand million years of geological time recorded in the rocks, have played an important part in moulding the surface of the Earth, producing extensive craters and other structures. The statistics of distribution of such large structures in space and time in the record can also be used, alongside astronomical and theoretical methods, to estimate the flux. These structures are also important because it has been suggested that immense-scale impactors have actually caused abrupt changes in the progressive development of life on Earth, causing mass extinctions. An immense impact structure is recognized in Yucatan, Mexico, on and offshore, of the same date as the major Cretaceous-Tertiary (K-T) mass extinction. The geological, geophysical and geochemical evidence for such an impact event is quite clear, but
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This 250-word extract was created in the absence of an abstract.
