Developments in Brief : Falling Satellite or Meteor Set Off Bomb Test Seismometers, Scientist Says

It was either a meteor or a falling satellite streaking across Canada that set off a sonic boom last year that was detected by seismometers used to monitor Soviet and U.S. nuclear bomb tests, a Canadian scientist said last week.

Seismometers, which are widely used to measure earthquakes, have detected ground motion from meteors striking Earth before, but not sonic shock waves from one, said Frank M. Anglin, an Ottawa-based seismologist for the Geological Survey of Canada.

The glowing object that streaked across the Northwest Territories shortly before dawn in September also could have been a satellite burning up, Anglin said at the Seismological Society of America’s annual meeting in Santa Barbara.

Canada and Britain built the 17 seismometers near Yellowknife, Canada, in the early 1960s to detect whether Soviet, U.S. and other nuclear bomb tests were in compliance with a possible comprehensive test ban treaty, he said.

After a Yellowknife resident reported the glowing object in the sky, scientists found their seismometers had recorded shock waves at the time. But those waves were not the type that would be caused by an object hitting the ground.

Further analysis showed that the seismic signals were caused by a sonic boom generated as the object streaked northeastward at nearly 27,000 m.p.h. about 28 miles above the Earth, Anglin said.

Because the object was so high, “nobody heard the boom. It didn’t shake anything,” he said.

Anglin said there is no way to calculate the object’s size because it either disintegrated in the atmosphere or crashed far from where it was seen.