Evidence for asteroidal origin of the Tunguska object

The progress in the understanding of the Tunguska object is reviewed in the light of evidence presented in numerous recent investigations, which appeared following the publication of my 1983 paper on the objectʹs proposed asteroidal nature. The issues addressed extensively in the present review involve: (i) the fundamental characteristics of the event, such as the objectʹs energy, altitude and velocity at the time of its terminal explosion and the dynamic pressure involved; (ii) the problem of atmospheric fragmentation of very massive impactors and the implications for their ablation and deceleration; (iii) new analysis of the orientation of the Tunguska objectʹs heliocentric orbit based on the best data on the apparent radiant of the fireballʹs atmospheric trajectory; and (iv) comparison with the findings of other recent investigations, including compositional studies. Also employed in the arguments are the results now available on the impacts of comet Shoemaker-Levy 9ʹs fragments into Jupier and the findings of a recent comparative study of two huge fireballs (one cometary, one stony, both involving impactors several meters across) observed with the cameras of the European Network of fireball monitoring. It is concluded that hypotheses based on presumed cometary origin of the Tunguska object encounter unsurmountable difficulties and that the interpretation of the event as a fall of a small stony or carbonaceous asteroid is not only plausible, but virtually certain.