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 World's End. Story by Charles E. Reineke.

 

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It came without warning some 65 million years ago, an unnamed and unwelcome visitor from deep in space. By the time it plowed into the Yucatan Peninsula, scientists estimate the six-mile-wide mass of rock and mineral was traveling as fast as 20 kilometers per second, more than 50 times the speed of sound.

This wasn't the first time the Earth had absorbed a major asteroid impact. But our planet had never experienced anything quite like this. According to a computer model developed by researchers at the Los Alamos National Laboratory, the asteroid's energy at touchdown would have equaled the force of 300 million nuclear weapons. "Immediate effects," the study found, "would include an eardrum-puncturing sonic boom, intense blinding light, severe radiation burns, a crushing blast wave, lethal balls of hot glass, winds with speeds of hundreds of kilometers per hour, and flash fires." Soon thereafter tsunamis, some perhaps 1,000 feet high, would have drowned huge swaths of land, even as the dry land burned. Within hours vast clouds of dust and soot would have blocked out the sun, plunging the entire planet into darkness and cold.

Welcome to the world's worst day, says Ken MacLeod, a professor of geological sciences at MU. "As you can imagine, slamming a six-mile wide rock into the Earth is going to be pretty destructive."

Just how destructive, however, remains a point of contention. The majority of scholars, MacLeod among them, believe that this cataclysmic impact drove almost every living thing on the planet to extinction. Most famous among the casualties were the dinosaurs, those magnificent beasts that had ruled the Earth for more than 165 million years.

A handful of other scientists, however, are equally convinced that no single event, not even one as devastating as the Yucatan strike, could explain the great culling of plant and animal species at the end of the Cretaceous Period. Led by Princeton paleontologist Gerta Keller, these scientists have spent the past decade arguing that only a host of factors, including perhaps multiple asteroid strikes, could explain the mass extinction phenomenon. What's more, they say, the fossil record shows the Yucatan strike likely predated the dinosaurs' demise by some 300,000 years.

Getting at the truth has proven difficult, chiefly because the destruction wrought by the asteroid has led to ambiguities in the geological record. The much-studied strata near the impact site itself, the Yucatan's 110-mile-wide Chicxulub (pronounced CHEEK-shoo-loob) crater is particularly resistant to conclusive analysis. Now, thanks to a chance discovery by MacLeod and an international team working on a shipboard drilling rig some 2,800 miles from the crater, the picture is getting clearer.

       
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Published by the Office of Research.

©2007 Curators of the University of Missouri. Click here to contact the editor.