Tagish Lake meteorite
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The Tagish Lake meteorite impacted the Earth on January 18, 2000; reported sightings in the Tagish Lake area in the Yukon Territory and northern British Columbia, Canada were confirmed after more than 500 fragments of the meteorite were found on the lake's frozen surface. 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 and seismographs.
The pieces of the Tagish Lake meteorite were all deep red in colour and barely over one kg in size. 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.
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. 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.
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.
[edit] 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
