The theories put forth to account for the Tunguska event range from the scientifically plausible to the ridiculous to the intriguing. They included:
A fragmentary asteroid or meteorite that exploded in the atmosphere.
The nucleus of a comet that likewise exploded in the atmosphere.
An unusual tectonic event.
A tiny black hole that entered the Earth's atmosphere from outer space and imploded.
A chunk of antimatter that reacted with the matter of our planet.
A crashed UFO, the propulsion drive of which exploded.
A deliberate attack by extraterrestrials.
The result of a test of Nikola Tesla's wireless power transmitter.
Again, there's no definitive proof for any of these ideas, but let's consider each.
And of course add to that the new story about a UFO saving the planet!