Word: iridium
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...entire planet. It was such an asteroid (or an equivalent-size comet) that many scientists believe caused the extinction of dinosaurs some 65 million years ago. The primary evidence, discovered by the late physicist Luis Alvarez and his son Walter, a geologist, is a layer of the element iridium laid down in sedimentary rock at about the time the giant reptiles disappeared. Iridium is rare on the earth's surface but more common in asteroids...
...enormous chunk of space rock hit the planet, the Alvarezes theorized, it would have largely disintegrated, casting a pall of iridium-rich dust and other debris over the world that could have lasted for months. Deprived of sunlight by this all-natural version of "nuclear winter," plants -- and the animals that fed on them -- would have died in droves. And when the dust finally settled, the iridium it contained would have formed just such a layer as the Alvarezes found...
...blocked novelist, cynically teaching college lit. The new twist is that Cornell's death, not to mention several others, is motivated not by the usual lusts (money, sex, power) but by dark literary passions. How far we have come from 1949, when it was a boring old iridium shipment that set everyone's wheels spinning. How acute of D.O.A.'s creators to realize that in today's culturally aspiring America there probably are people who would kill to write a few immortal sentences...
...Alvarezes' staunchest critics has been William Clemens, a paleontologist at the University of California, Berkeley. After systematically sampling parts of the eastern Montana area, he declared that the layer of iridium and the bones of the last surviving dinosaur were too far apart to share any meaningful connection. Besides, he asked, why should the mammals have survived any Cretaceous catastrophe? Says he: "If you're going to have a nuclear winter killing off the dinosaurs, why didn't it kill off everything else...
Nonetheless, the evidence in favor of an impact was rapidly accumulating. Other geologists uncovered similar iridium deposits just above Cretaceous rock beneath the floor of the Atlantic Ocean and under the Raton basin in northeastern New Mexico. Additional analysis showed that the samples contained ratios of gold and platinum nearly identical to those found in meteorites. Furthermore, other sediment layers containing abnormally high amounts of iridium were discovered under both the Caribbean Sea and the Gulf of Mexico; these layers were deposited around the time of a smaller mass extinction that occurred more than 30 million years...