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Impact Erosion of Planetary Atmospheres: Some Surprising Results

Newman, William I. and Symbalisty, Eugene M. D. and Ahrens, Thomas J. and Jones, Eric M. (1999) Impact Erosion of Planetary Atmospheres: Some Surprising Results. Icarus, 138 (2). pp. 224-240. ISSN 0019-1035. https://resolver.caltech.edu/CaltechAUTHORS:20141024-094917470

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Abstract

We have investigated by analytical and computational means the effect of Cretaceous–Tertiary (K/T) size impacts (5×10^(30)erg, 9-km-radius bolide of 10^(19)g) on terrestrial atmospheres. We have extended analytically the approximate solution due to A. S. Kompaneets (1960,Sov. Phys. Dokl. Engl. Transl.5, 46–48) for the blast wave obtained for atmospheric nuclear explosions (idealized to isothermal atmospheres) to ideal adiabatic atmospheres and to data-based models of the Earth's atmosphere. For the first time, we have been able to obtain analytically the particle trajectories in an isothermal atmosphere. The outcome of this nonlinear analysis is that a massive impact (without the subsequent ejection of substantial mass) would only influence a column of ≈30-km radius in the Earth's atmosphere and that the shocked gas would be propelled up and against the column “wall,” but would not escape from the planet. We examined the validity of “hemispheric blowoff,” the hypothesis that all material in a hemisphere lying above a plane tangent to the point of impact radially accelerated outward and, if sufficiently energetic, would also be ejected. We adapted and used a state-of-the-art code (CAVEAT), a hybrid Los Alamos–Sandia Lagrangian–Eulerian finite difference scheme for multimaterial flow problems with large distortion and internal slip. In our CAVEAT calculations, the vapor cloud produced by the impact produces a shock that is orders of magnitude stronger than any previous use of such codes. We developed new methods to test the accuracy and convergence of CAVEAT for K/T size impact events, and it proved to be a robust tool. We explored a K/T size impact where the 9-km-radius bolide was vaporized and injected into the atmosphere and found no radial outflow in agreement with the analytic model but, instead, a 50-km-radius vertical column formed with only a small fraction of material reaching escape velocity—no more than about 7% of the vaporized bolide plus atmospheric mass will escape the gravitation of the Earth.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1006/icar.1999.6076DOIArticle
http://www.sciencedirect.com/science/article/pii/S0019103599960761PublisherArticle
Additional Information:© 1999 Academic Press. Received September 13, 1996; revised December 4, 1998. We thank the Institute of Geophysics and Planetary Physics at Los Alamos National Laboratory for support (IGPP Grant 605 to W.I.N. and E.M.D.S.) and NASA Grant NAGW-1941 to T.J.A. This work is Contribution 5668, Division of Geological and Planetary Sciences, California Institute of Technology. We are grateful to Mordecai Mac Low for an insightful discussion of an earlier version of the article. We are particularly grateful for the comments and discussion by two extremely conscientious referees, Kevin Zahnle and Gary McCartor. The article benefitted substantially from all of their suggestions.
Funders:
Funding AgencyGrant Number
Los Alamos National Laboratory (LANL) Institute of Geophysics and Planetary Physics (IGPP)605
NASANAGW-1941
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences5668
Issue or Number:2
Record Number:CaltechAUTHORS:20141024-094917470
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20141024-094917470
Official Citation:William I. Newman, Eugene M.D. Symbalisty, Thomas J. Ahrens, Eric M. Jones, Impact Erosion of Planetary Atmospheres: Some Surprising Results, Icarus, Volume 138, Issue 2, 1 April 1999, Pages 224-240, ISSN 0019-1035, http://dx.doi.org/10.1006/icar.1999.6076. (http://www.sciencedirect.com/science/article/pii/S0019103599960761)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50775
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:24 Oct 2014 18:11
Last Modified:03 Oct 2019 07:26

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