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Sulfur Clouds May Have Killed Dinosaurs : Science: Researchers at JPL and in Moscow theorize that the impact of a giant comet sent poisonous plumes into the atmosphere, causing deadly rains.

December 30, 1994|ROBERT LEE HOTZ | TIMES SCIENCE WRITER

The disaster would unfold in predictable stages. At first, the immense sulfur fumes spewing from the crater would combine with oxygen to form sulfur dioxide. Rising high into the atmosphere, the sulfur dioxide would react with ultraviolet light and water vapor to form sulfuric acid.

The resulting acidic clouds, like those on Venus, would be thick enough to cut the amount of sunlight reaching earth's surface by about 20%, the researchers said. That is enough to drop temperatures worldwide by more than 20 degrees Fahrenheit.

"The unique aspect of this is the unusual site with the sulfuric element in the ground," Baines said. "The asteroid not only caused the largest known impact on Earth, but the asteroid hit the one spot on Earth that would cause a worldwide cataclysm," he said. "Only 5% of the earth has this kind of sulfur-bearing rock."

More on Science: * From the secrets of DNA to volcanoes on Venus, the TimesLink on-line service has a wide-ranging collection of articles on the sciences. Sign on and "jump" to keyword "science."

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Killer Asteroid? Scientists suspect that dinosaurs may have succumbed to the sulfurous atmosphere created when an immense asteroid smashed into a unique region of the Yucatan Penninsula that is unusally rich in brimestone, leaving a crater 125 miles in diameter. The sulfer fumes released by the impact would have been enough to cause a global winter lasting decades.

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