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SKY & TELESCOPE'S NEWS BULLETIN - JANUARY 21, 2000
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METEORIC BLAST OVER CANADA

A chunk of interplanetary debris slammed into Earth's atmosphere over
western Canada on January 18th, exploding with what impact specialist
Alan Hildebrand (University of Calgary) calls "one of the largest ever
airbursts detected over land." The daylight event occurred at 16:43:26
Universal Time (8:43 a.m. Pacific Standard Time) at 60.25 deg. north,
134.65 deg. west -- a little south of Whitehorse, British Columbia.
Sensors aboard defense satellites suggest that the airburst unleashed
energy equivalent to at least 2,000-3,000 tons of TNT about 25
kilometers above the ground. Residents of Whitehorse observed a
lingering dust cloud for 2 hours. According to Hildebrand, the
impactor was most likely a stony object. He asks eyewitnesses of the
event to contact him at 403-220-2291 (hildebra@geo.ucalgary.edu).

Later that day, amateur astronomers in the surrounding region noticed
an unusual display of noctilucent clouds hanging low in the western
sky after sunset. A "webwork of interwoven strands" formed a cloud
band was about 15 deg. across, notes Michael Hoskinson of Edmonton,
Alberta, creating "a silvery radiance that far outshone the dying sky
light." The meteoric dust particles left in the stratosphere
apparently served as condensation nuclei for the dramatic cloud
formation. "Noctilucent clouds normally occur in June or July only,"
explains meteorologist Alan Whitman, who observed the band while
driving to his home in Penticton, British Columbia.