The Galactic Theory of Mass Extinctions: an Update |
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| Authors: | Michael R Rampino |
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| Institution: | (1) NASA, Goddard Institute for Space Studies, New York, New York 10025, USA;(2) Earth & Environmental Science Program, New York University, New York, New York 10003, USA |
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| Abstract: | Astronomical and geological evidence is consistent with the hypothesis that mass extinctions of life on Earth are related
to impacts of comets whose flux is partly modulated by the dynamics of the Milky Way Galaxy. Geologic evidence for impact
(ejecta and large impact craters) has been found at times of mass extinction events, and the record of large dated craters
shows a significant correlation with extinctions. Statistical analyses suggest that mass extinction events exhibit a periodic
component of about 30 Myr, and periodicities of 30 ± 0.5 Myr and 35 ± 2 Myr have been extracted from sets of well-dated large
impact craters. These results suggest periodic or quasi-periodic showers of impactors, probably Oort Cloud comets, with an
approximately 30 or 36 Myr cycle. The best explanation for these proposed quasi-periodic comet showers involves the Sun's
vertical oscillation through the galactic disk, which may have a similar cycle time between crossings of the galactic plane.
Further refinement of the model will depend on the identification and quantification of the dark matter component in the galactic
disk, and discovery and accurate dating of additional impact craters.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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| Keywords: | Mass extinction comet showers |
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