Tunguska event

Asteroids (and comets), however, can be mixed by coalescence with stony and icy bodies. If large enough, they may transport volatilizable material into earth s atmosphere (the Tunguska event is probably associated with an ammonia spike in the Greenland ice core record). The stony body can fall to the earth s surface but evaporates (in the Tunguska event there is speculation of cosmic carbon input on the other hand, nitrate increase as would be expected from NO formation by heating the atmosphere (see Chapters 2.6A.4 and 5.4.1) has not been found (Rasmussen et al. 1984, 1999, 2008). 

Journal Air Pollution Control Association 22, 537-543 Rasmussen, K. L., H. B. Clausen and T. Risbo (1984) Nitrate in the Greenland ice sheet in the years following Tunguska event. Icarus 58, 101-108 Rasmussen, K. L., H. I F. Ohlsen, R. Gwozdz and E. M. Kolesnikov (1999) Evidence for a very high carbon/iridium ratio in the Tunguska impactor. Meteorites and Planetary Science 34, 891-895... 

These events liave sporadically happened even in our history. The Meteor Crater of Arizona is tliought to liave been formed between 20,000 and -30,000 years ago [58], Explosion of Tunguska meteor in 1908 and collision of Comet Shoemaker-Levy 9 against Jupiter in 1994 are the representative great events in the history. 

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