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. Is there a hidden, but powerful, danger inside the seemingly harmless comet?
Please note that Popular Mechanics definition of "close to" is something different that most people's. At any rate, the key to this theory is that hydrogen and oxygen in the ice shard exploded upon entering the atmoshphere, resulting in the difficult-to-explain explosion 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."
Link to Original Source