Scientists may have identified the first specks of interstellar dust in material collected by the US space agency's Stardust spacecraft.
A stream of this dust flows through space; the tiny particles are building blocks that go into making stars and planets.
The Nasa spacecraft was sent to catch material streaming from Comet Wild/2 and return it to Earth.
But it also carried a collector for interstellar dust.
The material was gathered by the Stardust probe in a seven-year, 4.8-billion-km (2.9 billion miles) interplanetary voyage.