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20 years ago tonight, a little before midnight, a cosmic missile streaked above the Midwest. It startled witnesses across five states. It then exploded with the force of perhaps 500 tons of TNT, raining shrapnel on Park Forest, Illinois, near Chicago. Debris hit houses, cars, and a fire station. A several-pound fragment punched a hole in the roof of one of the houses, bounced around the top floor, and settled not far from the head of a sleeping teenager.
The missile was a small asteroid — a space rock. It slammed into Earth’s atmosphere at about 45,000 miles per hour. Its outer layers vaporized, forming a brilliant meteor. The pressure of its trip through the atmosphere then caused it to explode, raining fragments across the landscape — the most heavily populated region ever to be pelted by a major “rain” of meteorites.
Several dozen pounds of those chips have been recovered. Studies of them have shown that the original space rock was a fragment of a much larger asteroid that broke up about 470 million years ago. The original body was in the asteroid belt, between the orbits of Mars and Jupiter. It was made of rock, not metal.
There’s a lot of disagreement about details of the fragment that hit Earth. Estimates of its original size range from about four to 10 feet, and a mass of a couple of tons to about 15 tons — a big missile that exploded 20 years ago tonight.
Script by Damond Benningfield