Seven particles captured by NASA's Stardust spacecraft may be the first sample of dust from beyond the Solar System that has been brought back to Earth.

Andrew Westphal at the University of California, Berkeley, and his colleagues — with the help of 30,714 citizen scientists around the world — scanned more than 1 million images of tracks left by particles on Stardust's collectors. They identified seven candidates with a surprising variety of crystal structures and elemental compositions.

These particles could help to explain the origin and evolution of interstellar dust, which current astronomical observations can only guess at.

Science 345, 786–791 (2014)