Tuesday, March 13, 2007

Meteorite Hazards in the Home

Last Monday morning, a space object of some sort crashed through the bedroom window of David and Dee Riddle’s home in Bloomington, Illinois. Geologists from Illinois State University (ISU)) who have examined the object are skeptical as to whether it is a true meteorite or perhaps a piece of "space junk" left behind by a satellite or spacecraft. While Robert Nelson notes that the object's density indicates a possible iron-nickel composition common to asteroids and the Earth's core, James Day finds the jagged ridge along one side of the object more typical of a manmade object. Fellow blogger Decrepit Old Fool voted with Dr. Day for the "space junk" hypothesis.

Regardless of its age and ultimate origin, the space object flew through Dee Riddle's window at a high velocity and lodged itself into a computer desk made of particle board. Now at ISU's geology department for analysis, the Bloomington "meteorite" weighs 402.41 grams and measures about 3 inches (7.6 cm) long by about 2.5 inches (6.35 cm) across and about half an inch (1.3 cm) thick. While the newspaper unfortunately converted the measurements to inches foran American readership, my back conversion suggests a volume of 62.7 cm3 and a density of 6.4 g/cm3. This is far denser than any rocks found at the Earth's surface, which average from 2-3 g/cm3.

The Riddles can be thankful that their space object was smaller in volume than the Peekskill meteorite, which traveled straight through Michelle Knapp's car as it sat in her driveway in the early morning hours of October 9th, 1992. The Peekskill meteorite weighed 12.4 kg, although its "chondritic" composition would indicate a lower density somewhat less than 4 g/cm3. A chondritic meteorite recently found near Statesboro, Georgia reportedly weighed 2.7 kg (6 lbs). That meteorite is undergoing detailed analysis by Dr. Michael Kelley of Georgia Southern University, with preliminary results suggesting an "L" type (low iron) composition. The rest of us can be thankful that the Riddles were sincerely interested in advancing scientific knowledge about their space object rather than angling for financial gain as was apparently done by Harold Cannon, who discovered the Statesboro meteorite.

Meanwhile, NASA is cutting out their search of the heavens for all but the largest of asteroids that may be on track to collide with the Earth in coming centuries. Approximately three-quarters of the objects over a kilometer (about sixth-tenths of a mile) in diameter that cross the Earth’s orbit have been discovered, their orbits calculated, and the potential for global catastrophe ruled out. That search is continuing while the agency has decided to abandon the search for smaller objects which might also represent significant hazards to desks, windows, cars, houses, cities, power plants, cities, counties, states, or even entire continents.

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