The limitations of NEO-uniformitarianism |
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| Authors: | D I Steel |
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| Institution: | 1. Anglo-Australian Observatory, Private Bag, 2357, Coonabarabran, NSW, Australia
2. Department of Physics and Mathematical Physics, University of Adelaide, South Australia
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| Abstract: | The geological and biological sciences have gradually dispensed with the nineteenth-century concept of substantive uniformitarianism - or gradualism - whereby the physical and biological features of our planet are assumed to have been brought about by the long-term accumulation of small changes. The catastrophist alternative sees the changes as being wrought largely by discrete, exceptional events; one such type of event is an impact by a substantial asteroid or comet. It is argued here that scientists working on small solar system bodies generally still labour under a form of this gradualism, in that a conventional starting point is to presume a steady-state, and what is seen now is assumed to be diagnostic of the long-term average conditions. This is here termed NEO-uniformitarianism, the NEO referring to Near-Earth Objects. It is maintained herein that this area of science needs to revise its philosophical basis by allowing catastrophist principles to be entertained; that is, the presumption of a steady-state needs to be rejected until such time as evidence to support it is revealed. It is argued that the weight of evidence favours the contrary. For example, evidence is outlined for (a) Variations in the terrestrial cratering rate, disallowing any equating of the crater record with the presently-observed large impactor population; (b) The presence of significant NEO complexes which may be due to giant comet disintegrations within the last 20 kyr, hence solving the problem of the supply of short-period comets; (c) A misbalance between the present supply of meteoroids, there being too many to be supplied by presently-observed comets and also a surplus above the population needed to maintain the interplanetary dust complex; and (d) A substantial variation in the interplanetary dust flux in the past 20 kyr, as might be expected from (b and c). |
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