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Close encounters and collisions of comets with the earthA computer search for earth-approaching comets among those listed in Marsden's (1983) updated orbit catalog has identified 36 cases at which minimum separation distance was less than 2500 earth radii. A strong representation of short period comets in the sample is noted, and the constant rate of the close approaching comets in the last 300 years is interpreted to suggest the lack of long-period comets intrinsically fainter than an absolute magnitude of about 11. A comet-earth collision rate derived from the statistics of these close encounters implies an average period of 33-64 million years between any two events. This rate is comparable with the frequency of geologically recent global catastrophes which appear to be associated with extraterrestrial object impacts, such as the Cretaceous-Tertiary extinction 65 million years ago and the late Eocene event 34 million years ago.
Document ID
19840041102
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Sekanina, Z.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Yeomans, D. K.
(California Institute of Technology, Jet Propulsion Laboratory, Pasadena CA, United States)
Date Acquired
August 12, 2013
Publication Date
January 1, 1984
Publication Information
Publication: Astronomical Journal
Volume: 89
ISSN: 0004-6256
Subject Category
Astronomy
Accession Number
84A23889
Distribution Limits
Public
Copyright
Other

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