Cosmic connections: Imperial scientist locates the origin of cosmic dust

Monday 1 September 2008

The origin of the microscopic meteorites that make up cosmic dust has been
revealed for the first time in new research out today (1 September 2008).

The research, published in the journal Geology, shows that some of the cosmic
dust falling to Earth comes from an ancient asteroid belt between Jupiter and
Mars. This research improves our knowledge of the solar system, and could
provide a new and inexpensive method for understanding space.

Cosmic dust particles, originally from asteroids and comets, are minute pieces
of pulverised rock. They measure up to a tenth of a millimetre in size and
shroud the solar system in a thin cloud. Studying them is important 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.

The study’s author, Dr Mathew Genge, from Imperial College London’s Department
of Earth Science and Engineering, has trekked across the globe collecting cosmic
dust. He says:

“There are hundreds of billions of extraterrestrial dust particles falling
though our skies. 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 origin of the cosmic dust that lands on Earth has always been unclear.
Scientists previously thought that analysing the chemical and mineral content of
individual dust particles was the key to tracing their origin. But this study
suggests that a comparison of multiple particles gives better results.

To pinpoint the cosmic dust’s origin, Dr Genge analysed more than 600 particles,
painstakingly cataloguing their chemical and mineral content and reassembling
them like a complex jigsaw. Dr Genge comments:

Dr Genge's work locates the origin of some cosmic dust

“I’ve been studying these particles for quite a while and had all the pieces of
the puzzle, 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.”

Dr Genge found that the cosmic dust comes from a family of ancient space rocks
called Koronis asteroids, which includes 243 Ida, widely photographed by the
NASA Galileo probe. 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. Further analysis shows that the dust originates from a
smaller grouping of 20 space rocks within the Koronis family called Karin
asteroids. It comes from an ancient chondrite rock, common in Karin asteroids,
which was formed in space at the birth of the solar system.

Chondrite meteorites often fall to Earth and Dr Genge was able to match the
mineralogy and chemistry of the dust particles with chondrite meteorite samples
previously collected. He backed up the cosmic dust’s origin with infrared
astronomical satellite data which showed Karin asteroids grinding and smashing
against one another to create cosmic dust.

Dr Genge says his research holds exciting possibilities for a deeper
understanding of our early solar system. He concedes that analysing space dust
will never entirely replace space missions, but adds that we may not have to
visit so many different places. He concludes:

“This research is the first time we have successfully demonstrated a way to
locate the home of these important little particles. 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. 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.”