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Leonid Meteoroids Storm Toward Earth

SAN DIEGO--Astronomers, stargazers, and satellite operators are gearing up for the Leonid meteor shower in November, which may produce the heaviest bombardment of Earth's atmosphere by tiny meteoroids since 1966. The cosmic blizzard could knock out a few satellites, according to a report here yesterday at an American Astronomical Society meeting. Scientists also described plans to study the meteor storm in unprecedented detail from special airplanes.

The Leonids (see above) are spawned by Comet Tempel-Tuttle, which ejects dense swarms of dust as it nears the sun. That dust wafts along the comet's orbit, which Earth crosses every 17 November. Occasionally, Earth will pass through a dense knot of dust from the comet's most recent loops past the sun, creating brief but spectacular "storms" of thousands of meteors per hour. The last such storm cascaded over the western United States in 1966. Models predict somewhat less dramatic storms this November over eastern Asia and in 1999 over Europe, although the exact hours, locations, and intensities are uncertain. People in the U.S. will have to hit the road to see the show.

Satellite operators are bracing for the worst. Thousands of flecks much less than a millimeter wide may "sandblast" every satellite during the 2-hour storm, says planetary scientist David Lynch of the Aerospace Corporation in El Segundo, California. Although almost none of the speedy chunks will exceed a centimeter across, even millimeter-sized ones will pack the same punch as 22-caliber bullets, Lynch says. Such collisions will be rare, but they may disable a satellite or two--primarily via the electrical flare a meteoroid creates when it vaporizes into a conducting plasma. Such plasmas, Lynch says, can kill vital electronics. As a precaution, NASA will not fly the space shuttle at that time, Lynch notes, and the Hubble Space Telescope's operators will point its mirror away from the onslaught.

Meanwhile, astronomers will enjoy "our only chance in a lifetime" to plan airborne observations of a meteor storm, says Peter Jenniskens of NASA's Ames Research Center in Mountain View, California, because Earth's orbit will miss the thickest dust clouds next century. Two planes packed with cameras, spectrographs, and other instruments will fly parallel tracks out of Okinawa to spot as many Leonids as possible. Researchers hope to learn about the comet's composition and the possible hazards of next year's storm, Jenniskens says.