[meteorite-list] Cometary airbursts and atmospheric chemistry: Tunguska and a candidate Younger Dryas event, Adrian L Melott et al, 2009.10.04 to be in Geology, 13p text: Rich Murray 2009.11.07

From: Rich Murray <rmforall_at_meteoritecentral.com>
Date: Sat, 7 Nov 2009 22:11:09 -0700
Message-ID: <92AF9C22927146D19F1D443DD9524A98_at_ownerPC>

Cometary airbursts and atmospheric chemistry: Tunguska and a candidate
Younger Dryas event, Adrian L Melott et al, 2009.10.04 to be in Geology, 13p
text: Rich Murray 2009.11.07

http://cargo.ucsc.edu/coffee/2009/10/04/cometary-airbursts-and-atmospheric-chemistry-tunguska-and-a-candidate-younger-dryas-event-replacement/

Cometary airbursts and atmospheric chemistry: Tunguska and a candidate
Younger Dryas event [Replacement]
Adrian L. Melott (Kansas),
Brian C. Thomas (Washburn),
Gisela Dreschhoff (Kansas),
Carey K. Johnson (Kansas)
ArXiv #: 0907.1067 (PDF, PS, Other)
Comments: Accepted for publication in Geology.
Numerous minor revisions in wording; no change in conclusions

We estimate atmospheric chemistry changes from ionization for the 1908
Tunguska airburst event, finding agreement with nitrate enhancement in
GISP2H and GISP2 ice cores, noting an unexplained accompanying ammonium
spike.
We then consider the candidate cometary impact at the onset of the Younger
Dryas (YD).
The estimated NOx production and O3 depletion are large, beyond accurate
extrapolation, but the ice core peak is lower than predicted, possibly
because of insufficient sampling resolution.
Ammonium has been attributed to biomass burning, with a coincident nitrate
spike found at YD onset in both GRIP and GISP2 ice cores.
A similar result is well-resolved in Tunguska ice core data, but that forest
fire was far too small to account for this.
Direct input of ammonia from a comet into the atmosphere is adequate to
explain ice core data at the YD event, but not Tunguska data.
An analog of the Haber process with hydrogen contributed by cometary or
surface water, atmospheric nitrogen, high temperatures, pressures, and the
possible presence of catalytic iron from a comet could in principle produce
ammonia, accounting for the peaks in both sets of ice core data.

Tags: atmospheric nitrogen, minor revisions, sampling resolution, younger
dryas, gisp2 ice

http://arxiv.org/ftp/arxiv/papers/0907/0907.1067.pdf 13 pages
Received on Sun 08 Nov 2009 12:11:09 AM PST