Nitrate in the Greenland ice sheet in the years following the 1908 tunguska event

Abstract

The Tunguska event on 30 June 1908 has been subjected to much speculation within different fields of research. Publication of the results of the 1961 expedition to the Tunguska area ( Florensky, 1963) supports that a cometary impact caused the event. Based on this interpretation, calculations of the impactor energy release and explosion height have been reported by Ben-Menahem (1975), and velocity, mass, and density of the impactor by Petrov and Stulov (1975). Park (1978) and Turco et al (1981, 1982) , used these numbers to calculate a production of ca. 30 × 10 6 tons of NO during atmospheric transit. This paper presents a high-resolution study of nitrate concentration in the Greenland ice sheet in ca. 10 years covering the Tunguska event. No signs of excess nitrate are found in three ice cores from two different sites in Greenland in the years following the Tunguska event. By comparing these results with results for other aerosols generally found in the ice, the lack of excess NO 3 − following the Tunguska event can be interpreted as indicating that the impactor nitrate production calculated by Park (1978) and Turco et al. (1981, 1982) are 1–2 orders of magnitude too high. To explain this it is suggested, from other lines of reasoning, that the impactor density determined by Petrov and Stulov (1975) probably is too low.