Tunguska

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Not long after sunrise on June 30th, 1908, a celestial visitor paid a call on Siberia, near the Tunguska River. It slashed through the clear sky in seconds, shining brighter than the Sun and leaving a long, glowing trail. And at an altitude of about five miles, it blasted itself to bits. Years later, an eyewitness who was more than 30 miles away from the blast described it like this:

WITNESS: I suddenly saw the sky split in two, and fire appeared high and wide above the forest. I felt a great heat, as if my shirt was on fire... Then a strong thump sounded, and I was thrown a few yards and lost consciousness.... The crash was followed by a noise like stones falling from the sky, or guns firing. The earth trembled.... A hot wind blew past the huts. Later, we found that many windows had been blown out and the iron lock in the barn door had been snapped.

The cause of this commotion was probably a rocky asteroid the size of a house or bigger. As it plunged into the atmosphere it exploded, flattening hundreds of square miles of forest. Witnesses saw the blast from hundreds of miles away, and heard it from even farther.

Over the years, scientists have found little physical evidence of the asteroid -- only some tiny grains of material buried in the ground. So there's been a lively debate about the nature of the object that exploded, its size, and the power of the blast -- a debate that continues even now. We'll have more about that tomorrow.

Script by Damond Benningfield, Copyright 2008

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