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Terrestrial impact rates for long and short-period comets

Paul R. Weissman
Terrestrial impact rates for long and short-period comets (in Geological implications of impacts of large asteroids and comets on the Earth, Leon T. Silver (editor) and Peter H. Schultz (editor))
Special Paper - Geological Society of America (1982) 190: 15-24

Abstract

Terrestrial impact rates are calculated for long and short-period comets crossing the earth"s orbit. For a random long-period comet the impact probability is 2.2 x 10 (super -9) per perihelion passage and the most probable impact velocity is 56.6 km s (super -1) . Based on the sample of 20 observed earth-crossing short-period comets the mean impact probability is 6.6 x 10 (super -9) per perihelion passage or 8.2 x 10 (super -10) yr (super -1) , and the most probable impact velocity is 28.9 km s (super -1) . For the long-period comets, based on an estimated flux of 16 comets AU (super -1) yr (super -1) brighter than H (sub 10) = 11, this leads to an impact rate of 2.9 x 10 (super -7) yr (super -1) or a cratering rate of 0.06 x 10 (super -14) km (super -2) yr (super -1) for craters with diameter > or =10 km. Assuming a steady state number of approximately 800 short-period comets in earth-crossing orbits leads to an impact rate of 6.6 x 10 (super -7) or a cratering rate of 0.13 x 10 (super -14) km (super -2) yr (super -1) for 10 km or greater craters. The total cratering rate from both long- and short-period comets is about 15% of the observed rate derived from known terrestrial astroblemes, though there is substantial uncertainty in both estimates. The estimated cratering rate from earth-crossing asteroids (Shoemaker and others, 1979) is about twice the observed rate. Monte Carlo simulations of the dynamical evolution of the Oort cloud give estimates of the cometary flux rate in the early solar system on the order of 200 times the current flux.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 190
Title: Terrestrial impact rates for long and short-period comets
Title: Geological implications of impacts of large asteroids and comets on the Earth
Author(s): Weissman, Paul R.
Author(s): Silver, Leon T.editor
Author(s): Schultz, Peter H.editor
Affiliation: Jet Propul. Lab., Earth Space Sci. Div., Pasadena, CA, United States
Affiliation: Calif. Inst. Technol., Dep. Geol. Planet. Sci., Pasadena, CA, United States
Pages: 15-24
Published: 1982
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
Meeting name: Conference on geological implications of impacts of large asteroids and comets on the Earth
Meeting location: Snowbird, UT, USA, United States
Meeting date: 19810919Oct. 19-22, 1981
References: 38
Accession Number: 1983-039461
Categories: Geomorphology
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 1983
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