Terrestrial impactors at geological boundary events - Comets or asteroids?

Details Terrestrial impactors at geological boundary events - Comets or asteroids? Terrestrial impactors at geological boundary events - Comets or asteroids?

Apr 1985

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1985natur.314..517w&link_type=abstract

Nature (ISSN 0028-0836), vol. 314, April 11, 1985, p. 517, 518. NASA-supported research.

Mathematics

Logic

18

Asteroids, Comets, Craters, Geochronology, Impactors, Solar System, Companion Stars, Extinction, Interstellar Matter, Solar Orbits, Supernovae, Earth, Impacts, Comets, Asteroids, Extinctions, Periodicity, Source, Origin, Perturbations, Hypotheses, Cretaceous-Tertiary Event, Ages, Craters, Samples, Terrestrial

Scientific paper

In the present evaluation of evidence presented to date for a 26-28 million year periodicity in the extinction record and the age of large, well dated terrestrial impact craters, it is noted that no simple, one-to-one relationship emerges between major asteroid and/or comet impacts, siderophile anomalies, and biological extinction events. While impacts may indeed be the major extinction-triggering event in some or even most cases, either other major events, or secondary effects of the impacts, may be the actual extinction-causing mechanism. Long term obscuration of insolation, planetary cooling, or lethal atmospheric pollution may vary among extinctions, depending on the actual state of the planet and its biota during the geological period in question. The source of 28 million year-period asteroidal impactors, moreover, remains unknown and thereby casts doubt on the entire periodicity scenario.

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