Human Journey

Why’s It so Dusty Down Here?

Not every meteor that slams into Earth is a dino-killing whopper. Microscopic meteorites also find their way down to the planet’s surface on a regular basis, but there’s been some debate about where exactly they come from.

In the September 1, 2008, issue of Geology, Mathew Genge of Imperial College London reports that a massive collection of cosmic dust grains found in Antarctic ice originally came from the Koronis asteroids, an ancient family of space rocks in the Main Belt between Mars and Jupiter.


Koronis family asteroid 243 Ida and its moon, Dactyl


The minerals and chemicals inside these itteh-bitteh pieces of asteroid match what scientists had previously found in a small group within the Koronis family called the Karin asteroids. And sure enough, telescope observations of the Karin show those rocks are even now jiggling around and smashing into each other, producing dust.

According to Genge, the discovery means that some level of research into the origins and formation of the solar system can be accomplished without even leaving the ground.


“Out of the cosmic dust, a planet is born.”

—NASA/JPL-Caltech/R. Hurt (SSC)

“The answer to so many important questions, such as why we are here and are we alone in the universe, may well lie inside a cosmic dust particle,” Genge said in a university news release.

“Since they are everywhere, even inside our homes, we don’t necessarily have to blast off the Earth to find those answers. Perhaps they are already next to you, right here and right now.”

Existential contemplation aside, knowing where cosmic dust that reaches Earth comes from likely won’t put a damper on the various live or planned missions to fly past, land on, or smash into full-size comets and asteroids.

For example, two years after NASA’s Stardust mission came back to Earth loaded with cometary debris, scientists are making discoveries that are re-writing the very definition of a comet.

And in a few short days ESA’s Rosetta mission will make its closest approach to the asteroid Steins while en route to land on Comet 67 P/Churyumov-Gerasimenko in 2014.


An artist’s concept of the Rosetta lander, Philae, and accompanying orbiter

—Copyright European Space Agency

At about U.S. $980 million for the Rosetta mission, it’s tempting to ask if this is money wisely spent just to, as ESA puts it, “study the origin of comets, the relationship between cometary and interstellar material, and its implications with regard to the origin of the solar system”—especially if it turns out we could get much of the same information by taking a microscope into the right backyard.

What can missions like Rosetta tell us about our everyday lives, and what unimagined technologies might be born from the quest to understand rocky lumps and dirty snowballs? And are the answers ultimately, literally, blowing in the wind?

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