[See here for a news article from December previewing Melott’s March publication.]
I’m still unpacking these two brand new papers from Adrian Melott and A.E. Carlson comparing the atmospheric signals of the Tunguska Event and the start of the Younger Dryas, but they appear relatively positive from standpoint of the YDB impact hypothesis.
The Melott paper is protected, so I can only share the abstract, and have not yet paid for the full version. But the Carlson paper, which seems to be the subordinate study, is freely available and I have Scrbd it below.
More later…I am on my way to Disney World with the wife and kids!
Cometary airbursts and atmospheric chemistry: Tunguska and a candidate Younger Dryas event
Adrian L. Melott1, Brian C. Thomas2, Gisela Dreschhoff1 and Carey K. Johnson3
+ Author Affiliations
1Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA
2Department of Physics and Astronomy, Washburn University, Topeka, Kansas 66621, USA
3Department 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 NOx production and O3 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.