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Cometary delivery of organic molecules to the early earthIt has long been speculated that earth accreted prebiotic organic molecules important for the origins of life from impacts of carbonaceous asteroids and comets during the period of heavy bombardment 4.5 x 10 to the 9th to 3.8 x 10 to the 9th years ago. A comprehensive treatment of comet-asteroid interaction with the atmosphere, surface impact, and resulting organic pyrolysis demonstrates that organics will not survive impacts at velocities greater than about 10 kilometers per second and that even comets and asteroids as small as 100 meters in radius cannot be aerobraked to below this velocity in 1-bar atmospheres. However, for plausible dense (10-bar carbon dioxide) early atmospheres, it is found that 4.5 x 10 to the 9th years ago earth was accreting intact cometary organics at a rate of at least about 10 to the 6th to 10 to the 7th kilograms per year, a flux that thereafter declined with a half-life of about 10 to the 8th years. These results may be put in context by comparison with terrestrial oceanic and total biomasses, about 3 x 10 to the 12th kilograms and about 6 x 10 to the 14th kilograms, respectively.
Document ID
19900056330
Document Type
Reprint (Version printed in journal)
Authors
Chyba, Christopher F. (Cornell Univ. Ithaca, NY, United States)
Thomas, Paul J. (Cornell Univ. Ithaca, NY, United States)
Sagan, Carl (Cornell University Ithaca, NY, United States)
Brookshaw, Leigh (Yale University New Haven, CT, United States)
Date Acquired
August 14, 2013
Publication Date
July 27, 1990
Publication Information
Publication: Science
Volume: 249
ISSN: 0036-8075
Subject Category
SPACE BIOLOGY
Funding Number(s)
CONTRACT_GRANT: NAGW-1023
CONTRACT_GRANT: NGR-33-010-220
CONTRACT_GRANT: NGR-33-010-101
CONTRACT_GRANT: N00014-83-K-0610
CONTRACT_GRANT: NGT-50302
Distribution Limits
Public
Copyright
Other