Oct. 13, 2000 A fragile, charcoal-like meteorite that plummeted on to a frozen Canadian lake last January may represent the most primitive solar system material yet studied, according to new research reported in the 13 October issue of the international journal Science.
The Tagish Lake meteorite is a carbonaceous chondrite, a rare class of ancient meteorite that includes water-altered minerals and organic compounds. Carbonaceous chondrites make up only two percent of all meteorite finds.
Analysis of the meteorite's mineral composition and oxygen and carbon isotopes reported by Peter G. Brown at The University of Western Ontario, Canada and colleagues suggests that Tagish Lake may represent a new class of carbonaceous chondrites, more primitive than any yet found.
Using numerous eyewitness accounts, photographs, videos, and satellite data of the meteorite's fiery and dramatic entrance into Earth's atmosphere, the researchers also calculated Tagish Lake's origin, its path through space, and its average velocity. Brown and colleagues suggest that the meteorite came from the middle of the asteroid belt with an orbit intersecting the Earth's orbit. The asteroid belt is located between Mars and Jupiter.
Fragments of the Tagish Lake meteorite should aid scientists in their reconstruction of the early solar system environment, particularly the types and amounts of elements present in the original solar nebula.
Carbon analysis of the meteorite indicates that some of the carbon is contained in nanodiamonds, tiny particles of interstellar dust that were swirled into the solar nebula prior to the formation of the solar system. Tagish Lake may be richer in interstellar grains than any meteorite yet studied, according to the Scienceresearchers.
The first recovered pieces of Tagish Lake meteorite were recovered and remain frozen, which will help researchers examine the full range of volatiles and organic compounds on a primitive meteorite for the first time. These organic materials may yield clues regarding the original building blocks of life on Earth.
In a related Perspective article also published in Science, Jeffrey N. Grossmann of the U.S. Geological Survey says that Tagish Lake is the most significant recovered meteorite fall since the well-known Allende meteorite from Mexico and Murchison meteorite from Australia, both recovered in 1969.
Co-author Alan R. Hildebrand of the University of Calgary, Canada says that the best indication of the significance of the Tagish Lake recovery may be the receipt of dozens of requests from meteorite researchers around the world to study the new fall.
The other members of the research team are M. Mazur, T. Rubak-Mazur, M. Glatiotis, and J. A. Bird at University of Calgary, Canada; M. E. Zolensky at NASA Johnson Space Center, Houston; M. Grady at The Natural History Museum, London, U.K.; R. N. Clayton and T. K. Mayeda at University of Chicago; E. Tagliaferri at ET Space Systems, Camarillo, CA; R. Spalding, Sandia National Laboratories, Albuquerque; N. D. McRae, M. D. Campbell, R. Carpenter, H. Gingerich, E. Greiner, P. JA McCausland, and H. Plotkin at University of Western Ontario, Canada; E. L. Hoffman at Activation Laboratories Ltd., Ancaster, Canada; D. Mittlefehldt at Lockheed Engineering and Science Co., Houston; and J. F. Wacker at Pacific Northwest National Laboratory, Richland, WA.
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