A meteorite's pristine origins

12:34pm, September 25, 2001
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A rare, carbon-rich meteorite that fell into a frozen Canadian lake early last year (SN: 4/8/00, p. 235) ranks as the most pristine of such specimens ever found, report the researchers who conducted the first chemical analyses.

The Taglish Lake meteorite is classified as a carbonaceous chondrite, one of the first group of meteorites to have formed in the solar system. The rock contains buckyballs–soccerballshaped molecules made of carbon–filled with the inert gases helium and argon. The ratio of helium to argon that the scientists measured matches the ratio that astronomers calculate was present in the cloud of gas and dust that surrounded the young sun and provided the raw material for the planets.

That finding indicates the Tagish Lake meteorite has preserved chemical elements that developed or accumulated early in the history of the solar system, according to chemist Sandra Pizzarello of Arizona State University in Tempe and her colleagues. They report their findings in the Sept. 21 Science. The presence of buckyballs and other carbon molecules could hold clues to the chemical evolution that preceded life in the solar system.

In contrast to the Murchison meteorite, another carbon-rich rock, the Taglish Lake object contains virtually no amino acids and only simple organic compounds. That could prove disappointing to scientists who had hoped to find in the meteorite a reservoir of materials essential to life, but the rock's chemical constituents "still might have contributed molecular precursors of biomolecules to the origins of life," says Pizzarello.

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