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Primitive extraterrestrial mud lands in British Columbia lake—oldest material in solar system


October 17, 2000: On January 18, 2000, a rare carbonaceous chondrite meteor exploded in Earth's atmosphere, scattering meteorite fragments of itself over the frozen surface of Tagish Lake in Northern British Columbia. The composition of this type of meteor is unusual in that it is rich in organic acids and clays, giving it a consistency more akin to dried mud than the other, more rock-like meteor types.

This brittle nature of chondrites means that they are rarely found, since most burn completely in the atmosphere; difficult to find, since they are invisible to metal detectors; and once found are often contaminated by water and terrestrial mud. The last chondrite known to land in 1965 resulted in only 1 gram of recovered material.

Jim Brook, who initially discovered the meteorites, wisely harvested about a kilogram of material without touching it with his bare hands, and stored the fragments in his freezer, preserving even their sulfurous smell.

Closer inspection of the recovered material by Physicist Peter Brown of the University of Western Ontario (Western), Alan Hildebrand (Geology, University of Calgary) and a multinational assembly of physicists, geologists, aeronautics experts and one philosopher (Howard Plotkin of Western, an expert in the history of meteoritics) revealed the presence of interstellar grains, including nanodiamonds and silicon carbide. These rare substances are derived from red giants and carbon stars that died long before our own solar system formed.

The relatively vast amount of information gained from multiple observations of the Tagish Lake fireball has allowed a calculation of the orbit of the parent meteoroid, which was roughly 200,000 kg in mass prior to its entry into the atmosphere. Its orbit stretched in an ellipse from midway between Jupiter and Mars to Earth. Brown, Hildebrand et al. published these and other observations of the Tagish Lake fall in the October 11 issue of Science.

Reference

Brown, P.G., A.R. Hildebrand, M.E. Zolensky, M. Grady, R.N. Clayton, T.K. Mayeda, E. Tagliaferri, R. Spalding, N.D. MacCrae et al. 2000. The fall, recovery, orbit and composition of the Tagish Lake meteorite: a new type of carbonaceous chondrite. Science 290:320–325.

Links

"Nine Planets" by Bill Arnett at the University of Arizona includes this page with meteorite pictures and links
http://www.seds.org/nineplanets/nineplanets/meteorites.html

PERMANENT—Projects to Employ Resources of the Moon and Asteroids Near Earth in the Near Term—have extensive information on asteroids, with an eye to mining them
http://www.permanent.com



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