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The 1908 June 30 Tunguska Event (TE) is one of the best studied cases ofcosmic body impacting the Earth with global effects. However, still today,significant doubts are casted on the different proposed event reconstructions,because of shortage of reliable information and uncertainties of availabledata. In the present work, we would like to revisit the atmosphericfragmentation of the Tunguska Cosmic Body (TCB) by taking into account thepossibility that a metre-sized fragment could cause the formation of the LakeCheko, located at about $9$~km North-West from the epicentre. We performedorder-of-magnitude calculations by using the classical single-body theory forthe atmospheric dynamics of comets/asteroids, with the addition of thefragmentation conditions by Foschini (2001). We calibrated the numerical modelby using the data of the Chelyabinsk Event (CE) of 2013 February 15. Our workfavours the hypothesis that the TCB could have been a rubble-pile asteroidcomposed by boulders with very different materials with different mechanicalstrengths, density, and porosity. Before the impact, a close encounter with theEarth stripped at least one boulder, which fell aside the main body andexcavated the Lake Cheko. We exclude the hypothesis of a single compactasteroid ejecting a metre-sized fragment during, or shortly before, theairburst, because there is no suitable combination of boulder mass and lateralvelocity.

The atmospheric fragmentation of the 1908 Tunguska Cosmic Body: reconsidering the possibility of a ground impact