No iridium anomaly after the 1908 Tunguska impact: Evidence from a Greenland ice core

— We have determined the abundances of Ir and other elements by neutron activation analysis on annual dust samples from an ice core from Site B in the Crete region in central Greenland covering the years 1905–1914. Iridium was detected in all samples, but we found no excess Ir above the background in the years following the Tunguska event. The lack of an Ir anomaly in the years after the Tunguska impact combined with the knowledge of the energy released during the impact and our present knowledge about stratospheric transport implies either a very low Ir content of the impactor or an exceptionally high geocentric velocity for the impactor.