What caused the Tunguska impact back in 1908?

The Tunguska explosion was caused by an object several tens of metres across that detonated in an airburst five to ten kilometres (3.1-6.2 miles) above Tunguska, Siberia, in 1908. Scientific opinion is divided as to whether the object was a meteoroid or a comet fragment. The former would have been a rocky mixture of iron ore and silicon oxides; the latter would have been mainly ice. The explosion was 1,000 times more powerful than the Hiroshima bomb so virtually all of the object was vaporised in the atmosphere.

Answered by Luis Villazon.