Word: comets
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...cold and dark, plants and animals perished. Compelling evidence of such cataclysms was revealed last summer: scientists confirmed that a giant crater, 176 km (110 miles) across, discovered under the northern tip of Mexico's Yucatan Peninsula was the likely impact point of a huge object, probably a comet, believed to have wiped out the dinosaurs and other forms of life 65 million years...
...January, for example, NASA released several radar images of the 6.4-km-long (4-mile) dumbbell-shaped asteroid Toutatis taken when it sped within 3.5 million km (2.2 million miles) of Earth -- a hairbreadth by astronomical standards. And while the warning that the 10-km-wide (6-mile) Comet Swift-Tuttle might slam into Earth in 2126 has now been retracted, it briefly caused genuine concern among many scientists...
...simply "did not want to talk about very large amounts of energy," says Canavan. "And therefore they wanted to ignore the problem." Some suggested heatedly, in leaks to the press, that pro-nuclear Star Wars scientists, frustrated by the down-sizing of their projects, were using the asteroid and comet threat as an excuse for revitalizing their jobs...
Once the nature of the approaching object is determined, explains physicist Edward Tagliaferri, a U.S. space program consultant, "it becomes easier to decide if you want a standoff explosion, a surface explosion or a subsurface explosion," If the asteroid or comet is small, it can be vaporized with a subsurface explosion, but for larger bodies, says Tagliaferri, "you'll probably have to nudge them into a new orbit." For an asteroid consisting largely of iron, he says, "you'd probably want to have a surface explosion...
FORGET ABOUT WHETHER AN ERRANT COMET, ANGRY volcano or invidious virus killed the dinosaurs 65 million years ago. Scientists have still not explained how the Saurian dynasty got started or why it dominated the earth for more than 150 million years. The discovery in northwestern Argentina of the fossilized skeleton of a 10-kg (22-lb.) carnivore that is 230 million years old may help paleontologists begin to solve the mystery. In the British journal Nature, researchers from the University of Chicago and the National University of San Juan, Argentina, report that the dog-size predator is the most primitive...