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Time - Man of the Year
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1993-04-08
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THE WEEK, Page 25HEALTH & SCIENCEFear of the Big Whopper
Scientists debate earth's vulnerability to asteroids -- then
and now
What's the world coming to? First, astrophysicists said
comets killed the dinosaurs. Then they implicated asteroids in
numerous other mass extinctions throughout the earth's history,
setting the stage for the awful news in October that the comet
Swift-Tuttle might crash into the planet in the year 2126.
The buildup to astronomical apocalypse grows ever more
dramatic. At the American Geophysical Union's meeting in San
Francisco, some respected researchers suggested that a large
space rock 10 to 20 km (6 to 12 miles) in diameter slammed into
the earth 250 million years ago and set whole continents adrift.
The announcement by Michael Rampino of New York University and
Verne Oberbeck of NASA-Ames Research Center stunned fellow
scientists, though many dismissed it out of hand. Some
skepticism seemed warranted. Rampino and Oberbeck rely heavily
on their supposition that certain rocks -- known as tillites and
long thought to be formed on the earth by glaciers -- were
actually the result of a celestial collision. But tillites are
so common that other researchers scoffed at the idea.
Finally a bit of good news: some astronomers have revised
calculations on Swift-Tuttle, and predict that the big comet
will breeze by us at a comfortable 15 million-mile distance. Of
course, there is always the possibility that some other
uncharted space rock may come crashing through the atmosphere.
Best keep an eye out.