COMETARY DELIVERY OF ORGANIC-MOLECULES TO THE EARLY EARTH
COMETARY DELIVERY OF ORGANIC-MOLECULES TO THE EARLY EARTH
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DOI：
10.1126/science.11538074
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发表时间：
1990-07-27
期刊：
影响因子：
56.9
通讯作者：
SAGAN, C
中科院分区：
文献类型：
--
作者：
CHYBA, CF;THOMAS, PJ;SAGAN, C
长期以来一直推测，地球在4.5 × 4.5的重轰击期间从碳质小行星和彗星的撞击中吸积了对生命起源重要的生命前有机分子。109至3.8倍。109年前对彗星-小行星与大气层的相互作用、表面撞击以及由此产生的有机物热解的综合处理表明，有机物在速度大于每秒10公里的撞击中无法存活，即使是半径小至100米的彗星和小行星也无法在1巴的大气中以低于这一速度的速度进行空气动力制动。然而，对于合理的致密（10巴二氧化碳）早期大气，我们发现4.5 ×109年前，地球以至少. apprx的速度吸积完整的彗星有机物。106至107千克/年，此后通量以约3.4的半衰期下降。108年。这些结果可以通过与陆地、海洋和总生物量的比较加以说明。3倍。1012公斤和约6倍。1014公斤。
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 .times. 109 to 3.8 .times. 109 years ago. A comprehensive treatment of comet-asteroid interaction with the atmosphere, surfact 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 .times. 109 years ago Earth was accreting intact cometary organics at a rate of at least .apprx. 106 to 107 kilograms per year, a flux that thereafter declined with a half-life of .apprx. 108 years. These results may be put in context by comparison with terrestrial oceanic and total biomasses .apprx. 3 .times. 1012 kilograms and .apprx. 6 .times. 1014 kilograms, respectively.