Ah, the Tunguska Event. In 1908, it levelled trees, vaporized wildlife and lit up the skys over Siberia. It has also baffled scientists, since the explosion was thought to have dug no crater. Until now.
A group of Italian scientists have found a lake occupying a small, bowl-shaped depression near the epicentre of the blast. Lake Cheko was likely created when a small fragment of the original meteor struck the ground. The majority of the meteor was destroyed by the airburst explosion that knocked down trees and terrified eyewitnesses- a blast equivalent to 20 million tonnes of TNT.
The theory is controversial. Dr Gareth Collins, a research associate at Imperial College London, UK, said:
"The impact cratering community does not accept structures as craters unless there is evidence of high temperatures and high pressures. That requires evidence of rocks that have been melted or rocks that have been ground up by the impact."
According to Collins, the crater is too shallow and lacks the tell-tale 'flap' of debris around the rim. It's also elliptical, which is strange.
More to the point: where is the 'impact cratering community', and how do I join?