Photo: Russian Mystery Blast Caused by Comet, Acid Rain Hints



The 1908 Tunguska blast flattens trees in remote Siberia in an artist's rendering.

The theory that the explosion was caused by a comet-based meteorite blowing apart in Earth's atmosphere is supported by evidence of acid rain in peat layers, scientists said at a July 2008 scientific meeting in Moscow.

Photograph courtesy Chris Foss/NGS


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