Heads Up for Meteorites

Article excerpt

Byline: The Register-Guard

The paradox of meteorites is they're extremely rare, but they're falling all the time.

That meteorite that streaked across the Siberian sky last Friday and blew to pieces, shattering glass and injuring more than 1,000 people, was the biggest event of its kind in a century. In 1954, a woman in Alabama became the only person known to have been hit by a meteorite. The risk of a meteorite ruining anyone's day is vanishingly small.

Yet between 37,000 and 78,000 tons of material reach the Earth's surface from space annually. Most of that is dust, but an estimated 18,000 to 84,000 meteorites bigger than 10 grams - the weight of four pennies - hit the Earth's surface every year.

The Siberian meteorite weighed an estimated 7,000 tons, which makes it a big one. The Willamette Meteorite, found near the Portland suburb of West Linn, weighed only 15 tons, and it's the largest meteorite ever found in North America and the sixth-largest in the world (the University of Oregon has a replica).

On the other hand, the Siberian meteorite wasn't really all that big. On the very same day as the Siberian light-and-sound show, an asteroid (or big meteor) more than 25 times as large, 150 feet in diameter and weighing 190,000 tons, passed within 17,000 miles of Earth, a near miss by astronomical standards. The asteroid that is believed to have wiped out the dinosaurs 66 million years ago was six miles in diameter.

Even the Siberian meteorite could have caused much more damage if it had fallen on a more densely populated area. If the asteroid that passed on the same day had a slightly different orbit, the effects of its impact could have been catastrophic. …