Scientists size up 'backyard' meteorite

July 24, 2005 at 4:15 PM
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CHICAGO, April 14 (UPI) -- U.S. scientists are studying a meteorite that literally landed in their back yard.

The meteorite punched through a rooftop in Park Forest, Ill., on the evening of March 26, 2003, and came from a larger mass that weighed about 1,980 pounds before it hit the atmosphere, according to scientific analyses by the researchers, at the University of Chicago.

The scientists calculated the original projectile's size based on measurements of the galactic cosmic rays that it absorbed. Measurements of a radioactive form of cobalt provided the meteorite's minimum size.

The Park Forest meteorite also showed signs that it had been highly shocked, probably when it was part of a rock that was broken from a much larger asteroid following a collision. The evidence for shock includes feldspar, a mineral that is formed only in high heat and pressure. Apollo astronauts recovered shocked specimens of the mineral from the moon. Impact shock was common in the early history of the solar system because of the large quantity of interplanetary debris then in existence.

Witnesses in Michigan, Illinois, Indiana and Missouri reported seeing the fireball that the meteorite produced as it broke up in the atmosphere.

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