Fragmentation of the Tunguska cosmic body

Abstract

The 1908 Tunguska event is unique because it was observed by numerous local residents. In addition, the surroundings of the epicenter were carefully studied by numerous expeditions. This allows us to single out the following features of the interaction of a cosmic body with the atmosphere: (1) the head of the flying object was ≥2 ​km in size; (2) the flight was accompanied by sounds similar to firing from a machine gun; (3) near the epicenter, the object was moving at a speed of <3 ​km ​s−1. To explain these features, a model of the cometary nucleus is proposed, and the fragmentation of the comet in the atmosphere is considered. It is assumed that the cometary nucleus is a multi-layered porous structure consisting of granules weakly connected to each other. The layers are separated by gas-tight shells. The fragmentation of such structure is closely connected with the sublimation of water and volatiles. A rapid phase transition from a solid to a gaseous body releases and throws out grains with refractory components. This explosive release of matter results in flares and loss of kinetic energy by the object. The calculations shown that under certain conditions, the Tunguska cosmic body with a mass of (3–4) ·109 ​kg could slow down and approach the Earth’s surface, retaining half of the original mass.