Tagish Lake (meteorite)

Meteorite
Name= Tagish Lake


Image_caption=
Image_width=
Type= Chondrite
Class= Carbonaceous chondrite
Group= C2 ungrouped
Structural_classification=
Composition=
Shock= S1
Weathering=
Country= Canada
Region= British Columbia
Lat_Long= coord|59|42|16|S|134|12|5|E|display=inline,title [http://tin.er.usgs.gov/meteor/metbull.php?code=23782 Meteoritical Bulletin Database: Tagish Lake] ]
Observed_fall= Yes
Fall_date= January 18, 2000 08:43:42 pst
Found_date=
TKW= 10 kg


Image2_caption=

History

The Tagish Lake meteorite impacted the Earth on January 18 2000 at 16:43 UT. The reported sighting of a fireball in the Tagish Lake area in the Yukon Territory and northern British Columbia, Canada was followed-up by gathering more than 500 fragments of the meteorite from the lake's frozen surface. Post-event atmospheric photographs of the trail left by the associated fireball and U.S. Department of Defense satellite information also yielded the meteor trajectory [cite journal |last=Brown |first=Peter G. |coauthors=Alan R. Hildebrand, Michael E. Zolensky, Monica Grady, Robert N. Clayton, Toshiko K. Mayeda, Edward Tagliaferri, Richard Spalding, Neil D. MacRae, Eric L. Hoffman, David W. Mittlefehldt, John F. Wacker, J. Andrew Bird, Margaret D. Campbell, Robert Carpenter, Heather Gingerich, Michael Glatiotis, Erika Greiner, Michael J. Mazur, Phil JA. McCausland, Howard Plotkin, Tina Rubak Mazur |title=The Fall, Recovery, Orbit, and Composition of the Tagish Lake Meteorite: A New Type of Carbonaceous Chondrite |journal=Science |volume=290 |pages=320-325 |date=2000-10-13 |url=http://aquarid.physics.uwo.ca/~pbrown/Science-reprint-pdf.pdf ] . Most of the stony, carbonaceous fragments landed on the Taku Arm of the lake, becoming encased in ice as they entered the lake's frozen surface. As the meteorite fell to Earth, it set off a wide array of satellite sensors, as well as seismographs.

pecimens

The pieces of the Tagish Lake meteorite were dark grey to almost black in color with small light-colored inclusions, and a maximum size of ~2.3kg. Except for a greyish fusion crust the meteorites have the visual appearance of a charcoal briquette. [Geological Survey of Canada. [http://cgc.rncan.gc.ca/meteor/images/tlm1.jpgMeterorite fragment photo] ] The fragments were transported in their frozen state to research facilities after they were pried from the lake's icy top layer. They were collected by researchers from the University of Calgary and University of Western Ontario, and were studied in collaboration with researchers from NASA. The meteorite is currently held in the collection at the University of Alberta.

Meteoroid

The Tagish Lake meteorite, before it impacted, was estimated at 4 metres in diameter and 56 tonnes in weight. However, when the fragments of the massive lump of rock were found, only 1.3 tonnes remained, meaning that around 97% of the meteorite had vaporised on its descent, during which the meteor finally exploded with around 1.7 kilotons of energy. Of these 1.3 tonnes of fragmented rock, only 0.1% was found and collected.

Origin

Analyses have shown that they are of a primitive age, containing unchanged stellar dust granules that may have been part of the cloud of material that created our solar system and Sun. The meteorite has proven to have come from the outer limits of the asteroid belt in our solar system.

Based on eye-witness accounts of the fireball caused by the incoming meteorite and on the photographs of the track, which it had left behind and which was visible for about half an hour, scientists have managed to calculate the orbit it followed before it impacted with Earth. Unfortunately, none of the photographs captured the fireball directly. Although both eye-witness evidence and photographs of the track are usually not very accurate, it was found that the Tagish Lake meteorite had a pre-entry orbit that brought it from the outer reaches of the Asteroid Belt. Currently, there are only six meteorites with accurately determined pre-entry orbits, based on photographs or video recordings of the fireball itself taken from two or more different angles.

ee also

* 773 Irmintraud, the asteroid that the Tagish Lake meteorite most likely came from

References

*"", Robert Dinwiddie, DK Adult Publishing, (2005), pg. 222.
*Mittlefehldt, D.W., (2002), Geochemistry of the ungrouped carbonaceous chondrite Tagish Lake, the anomalous CM chondrite Bells, and comparison with CI and CM chondrites, "Meteoritics and Planetary Science" 37: 703-712. [http://www.psrd.hawaii.edu/Dec02/TagishLake.html See summary of the article] .
*Mittlefehldt, D.W. (Dec., 2002) Tagish Lake-A Meteorite From the Far Reaches of the Asteroid Belt. "Planetary Science Research Discoveries". http://www.psrd.hawaii.edu/Dec02/TagishLake.html

External links

* [http://www.earthtimes.org/articles/show/11015.html Tagish Lake meteorite may have held early forms of life, believe scientists]
* [http://www.physorg.com/news65190953.html Ancient rock star finds a home at the University of Alberta]
* [http://aquarid.physics.uwo.ca/~pbrown/tagish/#intro Researchers' website]
* [http://www.geolsoc.org.uk/gsl/cache/offonce/geoscientist/features/pid/886;jsessionid=A887D8C58B3ADD4A5E3D4C1B34588374 The Geological Society] ; Article/Analysis
* [http://cat.inist.fr/?aModele=afficheN&cpsidt=810774 Brief Abstract]
* [http://cgc.rncan.gc.ca/meteor/tagish_e.php Tagish Lake meteorite specimen pictures]