Dusty Skies

Most of the dust in your home has an earthly origin: bits of dirt and pollen from the yard, skin cells from you and your pets, and even dust mites. But some of it probably comes from outer space — tiny bits of debris from comets and asteroids. In fact, a recent study says that almost 6,000 tons of that debris falls to Earth every year.

As comets orbit the Sun, they shed tiny grains of rock and dirt. And asteroids ram together, spraying similar grains into space. The particles spread out. And some of them enter Earth’s atmosphere and settle on the surface.

Estimates of how much reaches the surface vary by quite a bit. The numbers have been based on how much cosmic dust is found in sediments, how much is captured by high-altitude research aircraft, or how much is detected by spacecraft.

The recent study examined layers of ice in Antarctica. Over the last 20 years, researchers dug near Concordia Station, a European research base a few hundred miles from the south pole. They counted the number of cosmic dust grains found in different layers. When they projected the same rate across the entire planet, they came up with an annual fall of about 5700 tons.

They also compared the types of grains to models of how dust is scattered through the solar system. That told them that about 80 percent of the grains probably come from comets, with the rest from asteroids — extra sources of dust for your kitchen cabinets.
 

Script by Damond Benningfield