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Tagish Lake meteorite may hold clues to solar system formation.
By Robert Roy Britt
Senior Science Writer
posted: 02:00 pm ET
12 October 2000
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Cruising at 35,000 miles (56,325 kilometers) per hour, the object zoomed in over Earth's poles, hitting the lower layers of our atmosphere near the Yukon-Alaska border.
The entry angle was shallow, about 16 degrees from the horizontal, causing an unusually long "shooting star" that lasted some 15 seconds, according to eyewitnesses. The real show started about 56 miles (90 kilometers) up, when the meteor began to flatten out.
"The object fragmented heavily in a series of detonations starting at 44 kilometers (27 miles) altitude in the Yukon and ending in a final large burst at 33 kilometers (20 miles) altitude at the Yukon-British Columbia border," Brown said. "We estimate more than 95 percent of the mass of the initial object was consumed during these detonations and the rest of entry."
Freezing in the freshness
Brown figures only a few hundred kilograms of solid material, some no larger than grains of sand, actually made it to the surface. Travelling at 67 miles per hour (30 meters per second), many of the larger pieces shattered when they slammed into the ice. Others fell in snow and survived.
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Scientists digging up meteorite fragments on Tagish Lake. IMAGE: U. Calgary, U. Western Ontario |
The primordial information in meteorites is usually destroyed or contaminated, but because some of the Tagish Lake fragments were frozen, their ancient secrets likely appear intact, awaiting study. The largest piece recovered weighed about a half a pound (200 grams).
"Some evidence suggests it is the most primitive meteorite yet examined," Brown said. "If this proves true in subsequent detailed examination, the real impact of Tagish Lake will not be truly apparent for many years after many studies."
Other researchers who have studied the meteorite say it is in a remarkable state of preservation, thanks in part to the fact that its entry into Earth's atmosphere was slower than many space rocks. It has more carbon, including organic material, than researchers have ever seen.
"Its unusual composition, plus the fact that it has been kept cold since its fall, means that we may learn things about chemistry in the solar nebula that we never knew before," said Alan Hildebrand of the University of Calgary's Geology Department.
"We are still in very early days studying this meteorite and I expect that things will be learned that we do not yet anticipate," Hildebrand said. "I expect that study of this material will be quite intensive for one to two years after samples are widely distributed." | | | |
