It came from outer space - and likely disintegrated over northeastern Oregon (2/23/2008)

People in at least four states and a Canadian province saw a bright fireball streaking across the Pacific Northwest sky in the early hours Tuesday but, contrary to some reports, there was no collision with the ground, University of Washington scientists said.

Using readings from instruments in the Pacific Northwest Seismic Network, the scientists determined the object, called a meteoroid, disintegrated above the Blue Mountains about 25 miles north of Lagrande, Ore., at an altitude of about 19 miles.

Witnesses in Washington, Oregon, Idaho, Montana and British Columbia reported the fireball about 5:30 a.m. Tuesday. At least one person said the object had exploded on impact in eastern Washington and another person in southeastern Washington was said to have felt tremors from the blast.

Stephen Malone, a UW research professor emeritus of Earth and space sciences and former director of the seismic network, worked with other researchers at the UW and the Pacific Northwest National Laboratory in Richland to determine the source of the explosion.

They were able to triangulate the location using readings from seismometers that are part of the regional network, though the meteoroid appeared to come in at a sharp angle, preventing a calculation of a precise trajectory.

Malone noted that the readings are likely to be off somewhat because the seismometer station closest to the point where the meteoroid disintegrated has been out of commission since late January.

Following another widely observed meteoroid in June 2004, UW seismologists were able to pinpoint the explosion just north of the town of Snohomish at 27 miles altitude.

Note: This story has been adapted from a news release issued by the University of Washington

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