NASA finds first ever particles of interstellar dust

A NASA spacecraft has brought back what could be the most exotic material on the planet - seven dust particles from beyond the Solar System.

The impact of a vaporised dust particle called Sorok can be seen as the thin black line in the upper corner of this aerogel sample.

Image: Westphal et al. 2014, Science/AAAS

A team of scientists have NASA have reported finding seven tiny dust particles on detectors carried by their Stardust probe. These incredibly rare particles - some of which look like tiny, delicate snowflakes - might have been created by a supernova explosion outside the Solar System millions of years ago, and if confirmed, they’ll be the first samples of contemporary interstellar dust we’ve ever found.

"They are very precious particles,” said one of the team Andrew Westphal, a physicist at the University of California, Berkeley's Space Sciences Laboratory, in a press release. 

NASA’s Stardust probe was launched into space way back in 1999 to find particles like this from interstellar space - the region that exists between the star systems of a galaxy - and on the tail of the comet Wild-2. In 2006, Stardust flew past Earth, dropping its detectors by parachute for analysis. 

It then took an international team of scientists and some 30,000 citizen scientists - nicknamed “Dusters" - to scan thousands and thousands of microscope images of the detectors to find the particles. "The largest of the particles was only a few thousandths of a millimetre across, considerably smaller than this full stop. Most of the specks weighed a few millionths of a millionth of a gram," says Ian Sample at the Guardian. 

The researchers describe the particles in the journal Science.

While Westphal cautions that further analysis needs to be done to confirm the origin of these particles, he says they’re much more diverse in their chemical composition and structure than initially thought. The small particles are very different from the larger, fluffier ones, which suggests that they have different histories.

"The fact that the two largest fluffy particles have crystalline material – a magnesium-iron-silicate mineral called olivine – may imply that these are particles that came from the disks around other stars and were modified in the interstellar medium,” said Westphal in a press release. "We seem to be getting our first glimpse of the surprising diversity of interstellar dust particles, which is impossible to explore through astronomical observations alone."