Look at the dust in here!

Space is a messy place not least because of all the broken down satellites, chunks of rock and UFOs, but it is thick with dust as well. Now, origin of some of this cosmic dust that pervades empty space and bombards satellites and the Earth itself as microscopic meteorites has been revealed for the first time in new research published this month. It turns out that much of the cosmic dust bombarding the Earth comes from an ancient asteroid belt between the planets Jupiter and Mars.

According to Mathew Genge of Imperial College London, cosmic dust particles are minute pieces of pulverised rock measuring up to a tenth of a millimetre across. Studying them is important, he explains, because their mineral content records the conditions under which asteroids and comets were formed over four and a half billion years ago and provides an insight into the earliest history of our solar system. As such, Genge has trekked across the globe collecting cosmic dust samples hoping to unlock their secrets.

Cosmic Spherule(Credit: Genge et al/Imperial College)

Cosmic Spherule(Credit: Genge et al/Imperial College)

There are hundreds of billions of extraterrestrial dust particles falling though our skies, Genge says, This abundant resource 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 expensive missions.

The precise source of cosmic dust that reaches the Earth has until now been unclear. It derives from asteroids and comets and earlier scientists thought that simply analysing the chemical and mineral content of individual dust particles would allow them to trace the origins of cosmic dust more precisely. However, Genge’s study published this month in the journal Geology hints that comparing hundreds of particles provides a much clearer picture.

Mathew Genge (Credit: IC website)

Mathew Genge (Credit: IC website)

Genge has now analysed more than 600 particles, painstakingly cataloguing their chemical and mineral content and reassembling them like a cosmic jigsaw.

I’ve been studying these particles for quite a while and had all the pieces of the puzzle, he says, but had been trying to figure out the particles one by one. It was only when I took a step back and looked at the minerals and properties of hundreds of particles that it was obvious where they came from. It was like turning over the envelope and finding the return address on the back.

Genge has now revealed that the majority of cosmic dust particles come from a family of ancient space rocks called the Koronis asteroids, which includes the well-known asteroid 243 Ida. The rocks are located in an asteroid belt between Mars and Jupiter and were formed around two billion years ago when a much larger asteroid broke into pieces.

More detailed analysis still shows that the dust originates from a specific grouping of some 20 space rocks within the Koronis family known as the Karin asteroids. The type of mineral from which the asteroids and the cosmic dust are composed is ancient chondrite rock. Genge points out that these rocks were formed in space at the birth of the solar system.

Chondrite meteorites occasionally fall to Earth so Genge was able to match their mineralogy and chemistry to his cosmic dust samples. Infrared astronomical satellite data confirms that collisions between the Karin asteroids can create cosmic dust.

Further reading

Geology, 2008, 36, 687-690

Dr Matthew Genge homepage

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