05 September 2007

New dinosaur-killer theory

ZUI this article from the San Francisco Chronicle:
Now comes a team of planetary scientists who say they've pinned down the specific space object that did in all those dinosaurs, and killed off half of all the other species on Earth at that time.

It was, say the scientists, one huge asteroid that broke up in a violent collision 160 million years ago, sending a massive fragment careening out of the asteroid belt and eventually into the Earth's crust. The impact kicked up a storm of dust, cold and darkness that shrouded the world like a nuclear winter - and goodbye dinosaurs.


In the journal Nature today a group headed by William F. Bottke, an asteroid expert at the Southwest Research Institute in Boulder, Colo., traces that impact back to one giant asteroid named Baptistina nearly 100 miles in diameter. Baptistina, the team of scientists say, was rammed by an unnamed asteroid at least 35 miles in diameter in a violent collision about 160 million years ago - give or take 20 million years.

The collision showered nearby space with at least 300 fragments bigger than 20 miles in diameter and more than 140,000 smaller asteroids, each one more than 3 miles around, Bottke contends.

The smaller asteroids are now known as the Baptistina family, and according to Bottke and his colleagues - David Vokrouhlicky of Chares University in Prague and David Nesvorny of Bottke's institute - it was one of those "refugees" from Baptistina that created the 110-mile-wide Chicxulub crater.

ZUI this article from Scientific American, as well.
The researchers say the same bombardment may also have blasted the 53-mile-wide lunar crater Tycho, formed about 109 million years ago during the shower's calculated peak.

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