The Tuguska event of 1908 is one of the most frequently “explained” events in recent history, trailing only the Kennedy assassination. The arXiv blog reports on the latest explanation of what knocked down all those trees without making a giant crater:
Now a new analysis by Edward Drobyshevski of the Russian Academy of Sciences in St Petersburg Russia claims to have solved these problems. Drobyshevski concludes that the object that hit in 1908 was a comet (as have many scientists before him). But unlike the others, he has been able to calculate that this comet hit the Earth’s atmosphere almost at a tangent and broke apart.
The larger part of this comet skipped off the atmosphere, back into an Earth-crossing orbit (we should expect to find it nearby, predicts Drobyshevski).The smaller part rapidly heated up above Russia before exploding in the atmosphere over Tunguska.
The key to why it left so little lasting damage is the nature of the explosion, says Drobyshevski. And the key to that is our improved understanding of the chemical make up of comets. He says the comet would have had a high hydrogen peroxide content and this would have dissociated explosively as it heated up to produce oxygen and water, breaking the comet apart. It was this explosion that devastated Tunguska.
It sounds like a reasonable explanation of the event. But then, so have the last three or four, so who knows?