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

Authors: Adrian L. Melott (Kansas), Brian C. Thomas (Washburn), Gisela Dreschhoff (Kansas), Carey K. Johnson (Kansas)

(Submitted on 6 Jul 2009)

Abstract: We estimate atmospheric chemistry changes from ionization at the 1908 Tunguska airburst event, finding agreement with nitrate enhancement in GIS2PH and GISP2 ice cores and noting an unexplained accompanying ammonium spike. We then consider the candidate Younger Dryas comet impact. The estimated NOx production and O3 depletion are large, beyond accurate extrapolation. A modest nitrate deposition signal exists in ice core data. The predicted very large impulsive deposition might be visible in higher resolution data.

Ammonium has been attributed to biomass burning, and found coincident with nitrate spikes at YD onset in both the GRIP and GISP2 ice cores. A similar result is well-resolved in Tunguska ice core data, but the Tunguska forest fire was far too small to account for this. Direct input of ammonia from a comet into the atmosphere is consistent with the spike for the candidate YD object, but also inadequate for Tunguska.

An analog of the Haber process with hydrogen contributed by the cometary or surface water, atmospheric nitrogen, high temperatures, pressures, and the possible presence of catalytic iron from a comet could in principle divert a variable fraction of the reaction products to ammonia, accounting for ice core data in both events.

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (physics.ao-ph); Geophysics (physics.geo-ph)

Cite as: arXiv:0907.1067v1 [astro-ph.EP]

Submission history

From: Adrian Melott [view email]

[v1] Mon, 6 Jul 2009 18:35:53 GMT (101kb)

http://arxiv.org/abs/0907.1067