The sky is falling - a little

Remember the story of Chicken Little? She ran around telling everyone the sky was falling. What she should have yelled was "Watch out for rocks from outer space!" That's something that happens all the time.

Robert Giegengack, a professor of earth and environmental science at the University of Pennsylvania, estimates that 50,000 tons of meteoritic material reaches earth each year.

Most meteorites come from the asteroid belt between Mars and Jupiter. Asteroids may be remains of a planet that once occupied that region. A very small number of meteorites come from our moon or from Mars.

What falls to earth are mostly tiny fragments or dust particles. But not always. A meteorite thought to be 160 feet across exploded into dust three miles above Tunguska Valley, Siberia, on June 30, 1908. An expedition to the site found 1,200 square miles of damage.

Most of us will never come across a meteorite while out rock hunting. That's because we don't know where to look. Michael Lipschutz, a professor of chemistry at Purdue University in West Lafayette, Ind., studies meteorites. He knows exactly where to find them: Antarctica. Why Antarctica?

First of all, the snow is brilliant white, so stony, dark objects show up well. And because the ice is so thick, the only rocklike objects likely to be on the surface are meteorites!

Scientists make yearly trips to Antarctica to collect specimens. So far, some 12,000 to 15,000 meteorites have been brought back and cataloged.

If you want to look for meteorites closer to home, search "where there isn't any 'trash' rock," Dr. Lipschutz says. A desert is good. Look for black or dark-brown debris that's smooth and scorched-looking. Some meteorites have indentations that look like thumbprints.

Lipschutz says people are fooled all the time by furnace clinkers. A clinker is the remains of coal burned at a foundry. Here's one way to tell the difference: "Ninety-five percent of all meteorites will attract a magnet, since they have molten nickel iron," he says. "Clinkers won't."

Why hunt for meteorites? Because "meteors are the poor man's space probes," he says. "They let us know what our own planet and the solar system were like when they were new."

If you're interested in outer-space happenings, you would probably enjoy this Web site: spaceweather.com.

(c) Copyright 2000. The Christian Science Publishing Society