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Earth, Moon, and Planets

, Volume 72, Issue 1–3, pp 433–440 | Cite as

Evolution, punctuational crises and the threat to civilization

  • S. V. M. Clube
Article
  • 16 Downloads

Abstract

The relationship between “punctuated equilibrium” and “impact crises” is critically examined in the light of our present knowledge of asteroids and comets. It turns out that the emphasis on relatively narrow epochs associated with occasional “NEO” impacts is probably misplaced. Rather priority should be given to the wider and more frequent epochs associated with multiple “NEO” debris impacts which result in so-called “punctuational crises” afflicting the planets. These comprise the global coolings, super-Tunguska events and generally enhanced fireball flux produced by the larger orbital debris whenever an active, dormant or dead comet fragments and produces a trail. Taken as a whole and in conjunction with the target, the response function is inevitably complex. Nevertheless we broadly expect that the strength of a punctuational crisis will vary as the progenitor comet mass, the inverse dispersion of its debris and the inverse delay since fragmentation. The encounter of P/SL-9 with Jupiter may be taken as representing an extreme punctuational crisis where the dispersion and delay were exceptionally small. The more familiar crises affecting the Earth with less extreme values of dispersion and delay, which have resulted in civilization being disturbed a good many times during recent millennia, are no less important however. Indeed, the next such threat to civilization ostensibly has a roughly 1 in 4 lifetime chance. Any support for the Spaceguard programme which detracts from consideration of these punctuational crises, whatever their strength, would seem now to be peculiarly wide of the mark.

Keywords

Response Function Present Knowledge Global Coolings Orbital Debris Debris Impact 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Kluwer Academic Publishers 1996

Authors and Affiliations

  • S. V. M. Clube
    • 1
  1. 1.Department of PhysicsUniversity of OxfordOxfordU.K.

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