Dec. 18, 2007 -- About 34,000 years ago, a herd of mammoths found themselves at the wrong place at the wrong time. Analysis of seven tusks, purchased from a Canadian fossils vendor, show the ancient beasts were blasted by an exploding meteor.
"The only reasonable explanation is that a meteor exploded somewhere near where these animals were standing," Richard Firestone, a nuclear analytical chemist at Lawrence Berkeley National Laboratory said at the American Geophysical Union conference in San Francisco.
Scientists aren't sure if the animals died from their wounds, although the populations of several ice-age beasts decreased dramatically at about the same time of the suspected meteor strike. At least one creature, a bison, did survive, as its skull shows bone grew in after a fragment embedded, Firestone said.
"It was certainly a bad day," he said.
An amateur scientist, Allen West, got the idea to look at fossils for meteorite fragments in an attempt to find evidence of what wiped out the Clovis people of North America, as well as several large mammals, about 13,000 years ago.
After sifting through thousands of tusks at a Phoenix, Ariz., fossil show, he found one with a burnt hole in it and tested it with a magnet, as many meteors contain iron.
The magnet stuck. West bought the tusk for $200 and asked to look through the company's warehouse, which contained another 15,000 fossils. He found more evidence of micrometeorite impacts in a batch of tusks from eastern Siberia.
Some of the tusks had hundreds of tiny holes, made by burning fragments of the exploded meteor. The punctures all face the same direction, consistent with a blast from the sky.
Analysis by Firestone and colleagues confirmed that fragments in the tusks had high nickel-to-iron ratios and little titanium, indicating the shards probably did not come from Earth.
"We think the meteor exploded several miles up in the air, sending shrapnel in all directions," Firestone said. "Anything lying underneath it was likely to be injured or killed."
Scientists are continuing to refine analysis to determine when the mammoths were hit. They are also still on the lookout for another meteorite strike that occurred 65 million years ago, believed to be responsible for the extinction of the dinosaurs and a period of global climate change.
"It was pure serendipity that we found this," Firestone said.
The researchers hope museums, universities and private foundations will look through their collections of mammoth tusks and bones for signs of meteorite impacts. They also are looking at a meteor impact site in Canada that may be the source of the shards that pierced the mammoths. That meteor would have been about 550 yards in diameter.
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