Word: cometted
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...some time scientists have been moving toward the view that the extinction of the dinosaurs occurred after a giant comet or meteor struck the earth, filling the air with dust that shut out the sunlight for months. Now the theory is looking even better: a crater off the coast of Yucatan, known to be the right age (65 million years old) but thought to be too small to have been made by such a cosmic collision, has been discovered to be 185 miles across, not 110 as previously believed. The heavenly object that carved it out was plenty big enough...
That is when the earth will be passing close to the orbit of the comet Swift-Tuttle, which reappeared last year for the first time since 1862, swooped around the sun on Dec. 12 and headed back toward the outer solar system. Like all other comets, Swift-Tuttle sheds debris consisting largely of conglomerations of ice and dust, most of it boiled from the comet when it is in the vicinity of the sun. This material remains in orbit and gradually disperses along the comet's entire path, in effect forming a giant debris- laden tube in space. Each August...
These meteors are known as Perseids because they appear to emanate from the constellation Perseus, just as the Leonids, cast-off material from another comet, appear to radiate from a point in Leo. While most of the cometary debris consists of small particles, each tiny piece traveling at such high speed packs a mighty wallop capable of inflicting severe damage on anything it encounters. Consequently, satellites orbiting above the protective atmosphere during a heavy meteor shower are vulnerable. With this danger in mind, NASA prudently postponed last week's scheduled launch of the shuttle Discovery, which otherwise would have been...
...reason, he and many colleagues believe, may have been a mass extinction of many of the planet's species late in the Triassic period. It could have been caused by the impact of a massive asteroid or comet, perhaps, or by dramatic climate changes triggered as Pangaea separated to form distinct continents. As other animals disappeared wholesale, the dinosaurs evolved rapidly to fill vacant ecological niches. Says Sereno: "It's very difficult to argue that the dinosaurs had something the others didn't. Instead of evolving because they were better, maybe they evolved because there was a sudden vacuum...
...leading theory about what wiped out the dinosaurs used to be planetwide climate change; now it's something completely out of this world. Sixty-five million years ago, goes the story, at the very end of the Cretaceous period, an asteroid or comet smashed into the earth, throwing up a planetwide pall of dust. The sun was blotted out for months, killing most vegetation and starving the dinosaurs. The mammals, which had blown a chance during the last mass extinction, 150 million years earlier, rushed in to take over the suddenly vacant ecological slots...