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Thursday, 12 October, 2000, 21:40 GMT 22:40 UK
Fireball ignites scientific curiosity
Tagish Lake UWO/University of Calgary
The fireball lit up the sky over North America
By BBC News Online science editor Dr David Whitehouse

Scientists have revealed new data about a meteorite that could be one of the most primitive Solar System objects yet studied.

The space rock was recovered from the frozen Tagish Lake in Canada. The meteorite has aroused huge excitement among researchers because its fragments could help us understand better how the planets were formed.

The rock fell to Earth on 18 January, 2000. The exceptionally long and bright fireball was seen throughout the Yukon, Northern British Columbia, parts of Alaska, and the Northwest Territories.

Several dozen pieces of it have been retrieved. Importantly, the pieces were picked up still frozen, providing researchers with a unique opportunity to study organic compounds that may even have been the building blocks of life on Earth.

Tagish Lake UWO/University of Calgary
Preserved in ice: The rock opens a window to the past
The Tagish Lake meteorite is a so-called carbonaceous chondrite, a rare type of ancient meteorite that makes up only 2% of all meteorite finds. Unlike most rock found in the Solar System, it has not been changed by major heating sometime in its history and as such allows researchers a chance to study the very stuff that came together to form the Sun and the planets.

Analysis of the Tagish Lake meteorite, reported in the journal Science by Peter G Brown at the University of Western Ontario, Canada, and colleagues, suggests the rock may represent a completely new class of carbonaceous chondrite, more primitive than any yet found.

Using eyewitness accounts, photographs, videos, and satellite data of the rock's fiery and dramatic entrance into the Earth's atmosphere, the researchers have also calculated where the meteorite came from.

Its trajectory indicates that the space rock originated from the middle of the asteroid belt which lies between the orbits of Mars and Jupiter (about 300 million to 600 million kilometres/186 million to 370 million miles from the Sun).

Tagish Lake UWO/University of Calgary
Many researchers want to study the unique meteorite
Analysis of the carbon in Tagish Lake indicates that some of it is in the form of so-called nanodiamonds, tiny particles of interstellar material that were in the solar nebula, the cloud of gas and dust that came together to form the Solar System. Tagish Lake may be richer in interstellar grains than any meteorite studied before.

Jeffrey Grossmann of the US Geological Survey says that Tagish Lake is the most significant meteorite to come into the hands of scientists since the well-known Allende meteorite from Mexico and the Murchison meteorite from Australia, both of which were picked up in 1969.

Alan Hildebrand of the University of Calgary, Canada, says that the best indication of the significance of the Tagish Lake recovery can be seen in the receipt of dozens of requests from meteorite researchers around the world to study the new rock.

One fragment is already in the hands of British researchers at the Natural History Museum in London.

Tagish Lake UWO/University of Calgary
Many small fragments have now been recovered
One very interesting aspect of the Tagish Lake study is the compilation of detailed eyewitness accounts of the fireball.

Many people noticed smells at the time of the rock fall. These were frequently described as sulphurous, although hot metal and rock were also mentioned. And these smells were picked up by people many tens of kilometres from the drop zone.

About one in 10 also reported sound instantaneous to the fireball event. It might seem impossible that a noise can be heard concurrent with an object moving at speed many kilometres away, but scientists now believe this to be what they term an electrophonic effect.

It is possible that the twisting wake of a fireball might trap a magnetic field, creating very long radio waves that travel to the ground at the speed of light. The waves then interact with almost any object to produce a sound audible to the skywatcher.

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See also:

08 Sep 00 | Festival of science
Rare space rock in British lab
05 Sep 00 | Sci/Tech
Meteorite records early Solar System
19 Jan 00 | Sci/Tech
Robot hunts for space rocks
08 Jun 00 | Sci/Tech
A meteorite worth its salt
22 May 00 | Sci/Tech
Martian meteorite found in Oman
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