Journal Article

Impact cratering and the Oort Cloud

J. T. Wickramasinghe and W. M. Napier

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 387, issue 1, pages 153-157
Published in print June 2008 | ISSN: 0035-8711
Published online May 2008 | e-ISSN: 1365-2966 | DOI:
Impact cratering and the Oort Cloud

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We calculate the expected flux profile of comets into the planetary system from the Oort Cloud arising from Galactic tides and encounters with molecular clouds. We find that both periodic and sporadic bombardment episodes, with amplitudes an order of magnitude above background, occur on characteristic time-scales ∼25–35 Myr. Bombardment episodes occurring preferentially during spiral arm crossings may be responsible both for mass extinctions of life and the transfer of viable microorganisms from the bombarded Earth into the disturbing nebulae. Good agreement is found between the theoretical expectations and the age distribution of large, well-dated terrestrial impact craters of the past 250 Myr. A weak periodicity of ∼36 Myr in the cratering record is consistent with the Sun's recent passage through the Galactic plane, and implies a central plane density ∼0.15 M pc−3. This leaves little room for a significant dark matter component in the disc.

Keywords: astrobiology; Oort Cloud

Journal Article.  3473 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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