Scientists were able to spot seven interstellar dust particles, returned to Earth by Stardust in 2006, that represent primordial material from the birth of the solar system. It took 100 million searches to find these seven hits, which represent infinitesimally small bits of space dust that slammed into the spacecraft at 11,000 MPH. Much of the credit goes to the very patient volunteer members of the Stardust@Home project.
The Stardust mission was built to sniff the tails of comets that have ventured close to the sun. Comets are leftovers from the dawn of the solar system, so scientists figured studying them would yield clues about the solar system’s beginnings. But Comet Wild 2, Stardust’s main target, was not exactly a pristine specimen. It contained a wide range of organic compounds, evidence that the space rock had been baked and otherwise transformed on its journeys around the sun — interesting, but not primordial. To search for even more pristine materials, the mission team turned to interstellar dust, which Stardust had also collected.