Grains of cosmic dust from the solar system's birth found

Stardust Samples the Cosmos
Credit: NASA/JPL

We are all star stuff, it’s true. But that stuff, born in a supernova, underwent a whole lot of change on the way to becoming the sun, the Earth, and us. Raw ingredients can tell us more details about the solar system’s past, but they’re so tiny and fast that they're very tricky to find. Volunteers and scientists working on the 15-year-old Stardust mission have finally sifted out some of those ingredients.

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.

To do that, Stardust held out a tennis racket-sized dust catcher made of a spongy, barely-existent material called aerogel. Aerogel is 99.8 percent empty space and the rest is silica. When a speeding particle hits it, it becomes embedded in the aerogel and its entry track is preserved. Stardust captured some tiny particles — which, as Science Now points out, is no mean feat — and then sent them home in a space capsule that plummeted to the Utah desert. The sample return capsule is now at the Smithsonian Institution.

Stardust Sample Returns

But it turned out to be much harder to prove they were there, and that scientists had seen them all. The science team enlisted volunteer hunters, known as “dusters,” who joined the Stardust@Home project to help them look. Based in part on the SETI@Home crowdsourcing project, volunteers could log into a database and sift through it, looking for patterns. Our eyes and brains are much better at this pattern recognition than computers.

A few years later, volunteer Bruce Hudson found one particle, which he nicknamed Orion. Then last week at a planetary science conference, mission leader said they’d found seven total. Two of the particles weighed 3 trillionths of a gram apiece. That means you would need 100 billion of them to equal a single grain of sugar, Science says.

Now that they’ve been located, the science team wants to study these tiny particles in more detail, scrutinizing their isotopes to find out more about their origins — and all of ours.

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