Tagish Lake in the Yukon, the impact site of the "Tagish Lake" meteorite

History

The Tagish Lake^[1] 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 ^[2]. 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.

Specimens

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.^[3] 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.

See also

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

References

• Universe: The Definitive Visual Dictionary, 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. 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

• Tagish Lake meteorite may have held early forms of life, believe scientists
• Ancient rock star finds a home at the University of Alberta
• Researchers' website
• The Geological Society; Article/Analysis
• Brief Abstract
• Tagish Lake meteorite specimen pictures

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