Magazine article Science News

The Case of the Misclassified Meteorite

Magazine article Science News

The Case of the Misclassified Meteorite

Article excerpt

For 8 years, researchers had classified a meteorite found in the Allen Hills of Antarctica as a fairly ordinary chunk of rock--a fragment gouged from a familiar resident of the asteroid belt. Tucked away in a nitrogen-filled cabinet at NASA's Johnson Space Center in Houston, the meteorite has borne its commonplace label ever since its discovery in 1984.

That's how things stood until last October, when David W. Mittlefehldt, a geologist with Lockheed Engineering and Sciences Co. in Houston, examined a thin slice of the carefully preserved rock. A detailed analysis of its chemical composition has now stripped the 1.9-kilogram meteorite of its plebeian origin and assigned it celebrity status. The Allen Hills meteorite doesn't come from an asteroid, reports Mittlefehldt, it comes from Mars.

Only the 10th meteorite known to originate from the Red Planet, the Allen Hills rock is the first meteorite identified as having formed beneath the Martian surface. Because of its underground origins, it may provide a wealth of information on the geological processes that helped shape the planet, Mittlefehldt says.

When Mittlefehldt first sampled a section of the meteorite, he wasn't thinking about Mars. He simply wanted to take a close look at a meteorite that researchers had classified as a diogenite. This type of rock is believed to have come from a well-studied asteroid, 4 Vesta.

A devotee of diogenites for several years, Mittlefehldt analyzed the mineral content of the Allen Hills fragment, known as ALH84001. …

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