http://SaturnianCosmology.Org/ mirrored file
   For complete access to all the files of this collection
        see http://SaturnianCosmology.org/search.php
  ==========================================================


   Geology; April 2010; v. 38; no. 4; p. 355-358; DOI: 10.1130/G30508.1

   © 2010 Geological Society of America

Cometary airbursts and atmospheric chemistry: Tunguska and a candidate Younger
Dryas event

   Adrian L. Melott^1, Brian C. Thomas^2, Gisela Dreschhoff^1 and Carey
   K. Johnson^3 

   ^1 Department of Physics and Astronomy, University of Kansas,
   Lawrence, Kansas 66045, USA
   ^2 Department of Physics and Astronomy, Washburn University, Topeka,
   Kansas 66621, USA
   ^3 Department of Chemistry, University of Kansas, Lawrence, Kansas
   66045, USA

   We find agreement between models of atmospheric chemistry changes^
   from ionization for the A.D. 1908 Tunguska (Siberia region,^ Russia)
   airburst event and nitrate enhancement in Greenland^ Ice Sheet Project
   2 (GISP2H and GISP2) ice cores, plus an unexplained^ ammonium spike.
   We then consider a candidate cometary impact^ at the Younger Dryas
   onset (YD). The large estimated NO[x] production^ and O[3] depletion
   are beyond accurate extrapolation, but the^ ice core peak is much
   lower, possibly because of insufficient^ sampling resolution. Ammonium
   and nitrate spikes in both Greenland^ Ice Core Project (GRIP) and
   GISP2 ice cores have been attributed^ to biomass burning at the onset
   of the YD. 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
   for YD^ ice core data, but not for the Tunguska data. An analog of
   the^Haber process with hydrogen contributed by cometary or surface^
   water, atmospheric nitrogen, high pressures, and possibly catalytic^
   iron from a comet could in principle produce ammonia, accounting^ for
   the peaks in both data sets.^