Magazine article Science News

Mars Meteorite Poses Puzzling Questions

Magazine article Science News

Mars Meteorite Poses Puzzling Questions

Article excerpt

Mars meteorite poses puzzling questions

Researchers confirmed last week that a recently identified meteorite of Martian origin ranks as the oldest piece of the Red Planet known to have struck Earth. Radioactive dating indicates that the meteorite, a 1.9-kilogram rock designated ALH84001, formed about 4.5 billion years ago, during the solar system's infancy and shortly after the Martian crust formed. "This meteorite is giving us a look at Mars early in its history, when it was a warmer, wetter planet," says Everett K. Gibson of NASA's Johnson Space Center (JSC) in Houston. He and his collaborators, along with several other research teams, reported their findings at the annual Lunar and Planetary Science Conference in Houston.

Originally misclassified as a fragment gouged from an asteroid (SN: 3/26/94, p.206), ALH84001 has several intriguing properties, says Allan H. Treiman of the Lunar and Planetary Institute in Houston. For instance, among the 11 meteorites identified as chunks of Mars, ALH84001 has the highest concentration of carbonates.

The high carbonate content appears to support the long-held notion that water once flowed on Mars. Researchers speculate that carbonates crystallized within the meteorite when water rich in dissolved carbon dioxide percolated through rock just beneath the Martian surface.

In another finding, mass spectroscopy and electron microscopy reveal that ALH84001 contains polycyclic aromatic hydrocarbons (PAHs), report Kathie L. …

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