Red Flayer writes "Popular Mechanics is running a story that describes one of the more interesting explanations for the Tunguska explosion of 1908: 'Now, a controversial new scientific study suggests that a chunk of a comet caused the 5-10 megaton fireball, bouncing off the atmosphere and back into orbit around the sun. The scientists have even identified a candidate Tunguska object — now more than 100 million miles away — that will pass close to Earth again in 2045.' Note that Popular Mechanics' definition of 'close to' is somewhat different than most people's — the comet will be 3.8 million miles away at its closest. At any rate, the key to this theory is that hydrogen and oxygen in the ice shard exploded upon entering the atmosphere, resulting in the difficult-to-explain blast pattern (previous theories contend that the object must have 'skipped' on the atmosphere and then re-entered at the exact same spot). This would also, sadly, dash the theory that Nikola Tesla was responsible."