Gladysheva, O.G. The Descent of Pieces of the Tunguska Cosmic Body // Natural Science 5(5). 563–566. 2013. doi: 10.4236/ns.2013.55071
There is a hypothesis that fragments of a body from outer space fell to Earth as a result of the Tunguska event. During decades of investigations at the site of the disaster, stone or iron pieces from a cosmic body were not found. In spite of this, the number of adherents of this hypothesis is growing. For one thing, it was determined that the formation of swamp craters at the epicentre of the disaster is contemporary with the Tunguska event. Secondly, it was proven that the swamp craters are the result of thermokarst processes: their formation is connected with heat exchange in a permafrost zone. Now we can affirm that fragments of the Tunguska cosmic body (as a comet) with a mass of 10^(−3) ≤ M ≤ 10 kg reached the Earth’s surface, but they did not form craters. This conclusion was made from the isotopes and composition of element in peat deposits as determined by Kolesnikov’s group and L’vov.