In a paper in the journal Geology, Matt Genge, from ESE, reports the discovery that a large proportion of cosmic dust particles found in Antarctic ice.

ESE Solves Cosmic Dust Origins

In a paper in the journal Geology, Matt Genge, from ESE, reports the discovery that a large proportion of cosmic dust particles found in Antarctic ice, known as micrometeorites, are from the Koronis Asteroids of the main asteroid belt between Mars and Jupiter. This is the first time that the specific source of cosmic dust particles has been identified.

Cosmic dust is everywhere, it is on the streets, in our homes, even on our clothes. Each one of us is never more than a few feet from a dust particle from space, tiny pieces of rocks that could be from the moon, asteroids, comets, even Jupiter. Cosmic dust is important since these tiny pieces of rock allow us to study distant objects in our solar system without the multi-billion dollar price tag of a space mission. Despite the ubiquitous abundance of cosmic dust, however, it is difficult to know exactly where in space these little particles are from.

Genge's research describes that many dust particles from Antarctic ice have mineralogies and chemistries that closely match a type of meteorite known as ordinary chondrites, and on the basis of calculations have matching abundances of dust particles delivered to Earth from the Koronis Asteroids. Dust from Koronis has been seen in space by the Infrared Astronomy Satellite. It forms a cone-shaped band of dust that is fed at its outer edge by Koronis asteroids grinding themselves to pieces through collisions, and extends to the sun at the center of the cone, since dust in space spirals towards the sun due to the drag caused by sunlight.

The Koronis Asteroids are a family of rocky bodies formed around 2 billion years ago when a much larger asteroid broke into pieces. The most famous of these asteroids is 243 Ida and its tiny moon Dactyl, that was imaged by the NASA Galileo probe. Genge's work suggests that many micrometeorites are actually tiny pieces of around 20 smaller asteroids known as Karin group within the Koronis Asteroid Family and for the first time confirm that these stony asteroids are similar to ordinary chondrites, the commonest meteorites to fall on Earth. They show that the asteroid was heated early in its history similar to the internal heating of planets. They also suggest the asteroid contained water formed by the melting of ice.

On the discovery Genge says: “I’ve been studying these particles for quite a while and had all the pieces of the puzzle to work out their origins, but had been trying to figure out the particles one by one. Compositions and mineralogies are like fingerprints, and one fingerprint doesn’t make a good case, but a room full of fingerprints from the same culprit is pretty conclusive. It was only when I looked at data from hundreds of particles I realised where they came from. I was kind of like turning over the envelope and finding the return address on the back.”

Genge believes that cosmic dust will become increasingly important in the study of our Solar System. He says “With new analytical techniques we are now able to study the smallest pieces of rock in detail, which record the history of objects hundreds of millions of kilometres from Earth. To find the answers to questions such as why we are here and are we alone in the universe, we might not need to blast off the surface of the Earth, those answers might be already be lying at the fingertips of any one of us, inside a cosmic dust particle.”

Related Links

• Geology paper

Associated Personnel

• Matthew Genge