TY - JOUR
T1 - Cometary delivery of organic molecules to the early earth
AU - Chyba, Christopher F.
AU - Thomas, Paul J.
AU - Brookshaw, Leigh
AU - Sagan, Carl
PY - 1990
Y1 - 1990
N2 - It 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 109 to 3.8 x 109 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, we find that 4.5 x 109 years ago Earth was accreting intact cometary organics at a rate of at least ∼106 to 10 7 kilograms per year, a flux that thereafter declined with a half-life of ∼108 years. These results may be put in context by comparison with terrestrial oceanic and total biomasses, ∼3 x 10 12 kilograms and ∼6 x 1014 kilograms, respectively.
AB - It 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 109 to 3.8 x 109 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, we find that 4.5 x 109 years ago Earth was accreting intact cometary organics at a rate of at least ∼106 to 10 7 kilograms per year, a flux that thereafter declined with a half-life of ∼108 years. These results may be put in context by comparison with terrestrial oceanic and total biomasses, ∼3 x 10 12 kilograms and ∼6 x 1014 kilograms, respectively.
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U2 - 10.1126/science.11538074
DO - 10.1126/science.11538074
M3 - Article
C2 - 11538074
AN - SCOPUS:0025573714
SN - 0036-8075
VL - 249
SP - 366
EP - 373
JO - Science
JF - Science
IS - 4967
ER -