Phil Plait The Bad Astronomer is sceptical.
For those who don't know nearly 100 years ago back in 1908, something exploded at a height of 6 miles over a remote region of Siberia. The blast released 15 megatons of energyâ€”about a thousand times that of the atomic bomb dropped on Hiroshimaâ€”and flattened 770 square miles (2,000 square kilometers) of forest.
It was thought to be caused by an asteroid, but no crater was found. As a result the so called Tunguska event became a set piece in all sorts of crack pot crazy theories after that. It got used on xfiles a few times and at one point was blamed on a black hole.
Now some scientists have found what they think may be a crater consistent with the blast.