What’s in dust, and where does dust come from?

If you lived by the seaside, the tiny grains of dust you’d see drifting in a ray of sunlight might not have much in common with the dust you’d see from within a major city. What’s in dust, and where does dust come from?

What’s in dust depends mostly on what’s going on around you. The dust in a coastal cottage, for example, would tend to be on the salty side. Breaking waves and bursting bubbles release salts into the air, which would eventually wind their way onto your tabletops. But in the city, part of that fine coating at the edge of your shelves might have started out in a taxi’s tailpipe, or in a smokestack.

Despite the regional differences in dust, scientists still have a general idea of the major sources of dust on Earth as a whole. Much dust comes from volcanoes and fires, as well as from industrial sources like mines and refineries. The bulk of dust, though, seems to be fine bits of broken down dirt and rocks.

But in our homes, there’s another mother lode of dust: us! We’re all constantly shedding skin cells, which build up around us. Some household dust might even come from outer space. Cosmic dust is made of particles that originated in asteroid collisions.

As these fragments spiral slowly through space, some cross Earth’s orbit and eventually — in the form of dust — wind up on our window sills.

If you enjoyed this program, you may be interested in the following book:

  • Kenneth Pye. Aeolian Dust and Dust Deposits. NY: Harcourt Brace Jovanovich, 1989.

Tiny creatures called dust mites — relatives of spiders — feed on our lost skin. These dust mites shed their shells and leave behind waste, which further adds to the dust in our midst, no matter how much we clean up.

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