Word: asteroidal
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...danger is a comet or asteroid strike on the Earth. Thousands of chunks of cosmic rock enter the atmosphere of our planet every year. The vast majority burn up in the atmosphere, creating spectacular display for young lovers on lazy summer nights...
...asteroid that wiped out the dinosaurs 65 million years ago -- it threw megatons of dust into the air, blocking out the sun and putting the planet in a temporary deep freeze -- may have had company. French scientists have found rocky debris in the Pacific that's about the same age but probably came from a different object than the one that landed off Mexico's Yucatan coast. The implication is that an asteroid shower, rather than just a single asteroid, struck the earth...
...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...
...Shoemaker, with geologist Eleanor Helin, began the world's first systematic Earth-crossing-asteroid watch. When Helin left in 1982 to launch her own asteroid search, Carolyn, her three children grown, joined Gene. Since then they have been on the alert -- and on the run. Last fall, for example, they went to a conference in Ontario at the site of the 1.8 billion-year-old Sudbury Crater, which is 300 km (188 miles) wide. From there, they flew to Iowa City, Iowa, where Gene examined core samples from the nearby Manson Crater, 35 km (22 miles) across and about...