Comet/Asteroid Impacts and Human Society

pp 211-224

Physical Effects of Comet and Asteroid Impacts: Beyond the Crater Rim

  • H. J. MeloshAffiliated withLunar and Planetary Lab, University of Arizona

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Astronomical and geological investigations initiated in the past century have revealed that the Earth is continually subjected to the infall of a variety of solid solar system debris. Most of this debris is so small that it evaporates harmlessly, as it enters the Earth’s upper atmosphere at high speed. However, an occasional larger object survives atmosphere entry. Small examples of such objects result in meteorites on the surface of the Earth, with harmful consequences only for the rare individuals, who happen to be struck by them. More infrequent, but larger, objects can cause local or even global devastation. A recent report on the number and consequences of such impacts (Team 2003) proposes that the impact frequency can be computed as a function of the energy release, equal to the kinetic energy of the object before it strikes the Earth:
$$ T_{RE} (years) = 110E_{MT}^{0.77} $$
where T RE is the recurrence interval (in years) and E MT is the energy release in megatons of TNT equivalent (1 MT = 1015 cal ≈ 4.2 × 1015 J).