Washington scientist tracks meteor with video

November 11, 1992|By Douglas Birch | Douglas Birch,Staff Writer

After a meteorite creased the skies above Maryland like a tracer bullet and punctured the trunk of an old Chevy in New York, astronomer George Wetherill took up the cry of sportscasters everywhere.

Let's go to the videotape!

Dr. Wetherill, a planetary scientist with the Carnegie Institution of Washington, has begun assembling an eclectic collection of tapes of high-school football games and other outdoor events that occurred on the night of Oct. 9.

By studying tapes that recorded the meteorite's speed and direction, Dr. Wetherill and his collaborator, Peter Brown of the University of Western Ontario, hope to calculate the object's orbit.

Since the 1960s, astronomers have been able to trace the orbits of only three meteorites. All were measured following organized, large-scale experiments in the United States, Canada and Central Europe.

But the age of video has created new opportunities. "This has never been done before, we're out there on terra incognita," Dr. Wetherill said.

The research could help scientists trying to learn more about where meteorites come from. And it could aid astronomers studying giant "killer" asteroids, such as the one that may have slammed into the Yucatan peninsula 65 million years ago.

That impact is thought to have thrown up a massive cloud of dust that blocked out the sun for months and led to the extinction of the dinosaurs.

The October meteorite began to glow as it pierced the Earth's atmosphere about 45 miles above West Virginia, Dr. Wetherill figures. After streaking eastward for a few seconds, it landed in Peekskill, N.Y., at about 7:50 p.m. that Friday.

People from all over Maryland saw the celestial fireworks, flooding police and weather forecasters with anxious calls. Some meteorologists mistook the display for an unusual form of lightning. Many residents north of Baltimore missed the show, though, because severe thunderstorms were raking the area at the time.

A football-shaped chunk of interplanetary rock, weighing 22 pounds, punctured the trunk of a red 1980 Chevy Malibu owned by 18-year-old Michelle Knapp, and dug a 1-foot crater in the pavement.

The meteorite was moving at an estimated 10 miles per second, although the precise speed is something researchers hope to pin down.

Realizing that television stations and amateurs across the region could have recorded the event, Dr. Wetherill advertised for meteorite videos in computer bulletin boards and talked about his research with the Washington Post.

So far, he has secured copies of three videos and hopes to get his hands on another 22 tapes from across the Northeast, including North Carolina, Virginia and Pennsylvania.

One tape, widely shown on television, was shot by a man testing his new video recorder by photographing teen-agers cruising a Burger King on U.S. 50 in Fairfax, Va.

But the shot is only of the tail end of the meteorite's path. "What you need to do is get back as close as you can to the beginning of the path to get the velocity before it starts to slow down," Dr. Wetherill said.

The Peekskill meteorite, which is now in the hands of private collectors, fell during the annual Draconid meteor shower, but Dr. Wetherill doubts it was part of the same swarm. The meteorite traveled southwest-to-northeast at a low angle while the Draconids were falling from directly overhead.

If his tapes show evidence it was one part of the Draconid shower, he said, "that would be very exciting, because the Draconids are associated with a known comet, Giacobini-Zinner." No one has ever collected a large comet fragment. "If we had a piece of comet in a laboratory, that would be a fantastic thing," he said.

By calculating the meteorite's orbit, the scientist hopes to test a leading theory for how stony and metallic chunks of rock are knocked out of the asteroid belt between Mars and Jupiter and sent on a collision course with Earth.

Dr. Wetherill and others think there are two regions in the belt where the orbits are unstable because of the gravitational forces exerted by Jupiter. As the planet approaches, it pushes all the rocks in the belt. For some asteroids, the push comes at just the right time to exaggerate their elliptical orbits.

"It's like pushing a child in a swing," Dr. Wetherill said.

"If you do it at the right time, he goes higher and higher." Eventually, he said, the asteroids cruise toward Earth.

Anyone with videotape of the meteorite can reach Dr. Wetherill at the Carnegie Institution, 5241 Broad Branch Road N.W., Washington, D.C. 20015.

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