Sky Dust Keeps Falling on Your Head


Any time you go outside,you get pummeled by invisible storms of dust. Even on a perfectly sunny day, you inhale pieces of dead bugs. Floating specks of hair and pollen settle on your skin. Tiny chunks of comets might even fall on your head from outer space.

"Every time you sit on a bench, you're sitting on cosmic dust," says astronomer Don Brownlee from the University of Washington in Seattle. In fact, 6 million pounds of space dust settle on the planet every year, he says. "If you're outside during the day, you're probably going to get hit by a couple of things."

You might never notice the stuff falling all around you. But some scientists collect cosmic dust and other kinds of floating particles to learn about weather patterns, pollution, and the origin of the universe.

And now a new project is bringing sky dust studies down to earth: Maybe someday soon even you can help.

Studies of outer space have traditionally involved lots of expensive equipment. Brownlee and his colleagues, for example, send hi-tech airplanes more than 65,000 feet above Earth's surface. The aircraft fly at three-quarters the speed of sound for 50 hours or so, collecting cosmic dust on a sterile filter about the size of a deck of cards.

About half of what they pick up are micrometeorites-pieces of comets and asteroids about as wide as a human hair is thick. Back on Earth, the scientists analyze the space dust as a window into the past.

Meteorites are the only records we have of the origin of the universe, Brownlee says. "They date back in time to when the sun and Earth formed 4? billion years ago."