We're all made of star dust, as Carl Sagan famously observed. But the nature of that dust, long before it assembled into us, is a scientific mystery whose answer may lie in a box in a UC Berkeley lab.
A team of scientists there say they've captured the first samples of interstellar material -- seven super-tiny particles of precious rock, perhaps from far distant exploded stars -- that drifted into reach from beyond our solar system.
"This is the original stuff," said Andrew Westphal, a physicist at UC Berkeley's Space Sciences Laboratory and the lead author -- with 65 main co-authors -- of a report on the particles in the Aug. 15 issue of the journal Science.
We didn't need to travel to the distant galaxy to find them. That's too far to go. Instead, they were captured near Mars by the Stardust spacecraft that NASA launched in 1999 to sample the dust in a comet's wake.
A team of scientists, including Scott Sandford, an astrophysicist at NASA's Ames Research Center in Moffett Field, has been finely combing through the spacecraft's dust collectors.
Westphal cautioned that additional tests must be done before the team can say definitively that the Stardust probe returned to earth with debris from interstellar space.
But if they are, the particles could help explain the origin and evolution of matter that until now could only be guessed from astronomical observations.
Our bodies and all that surrounds us are just the detritus conceived from the materials of exploded stars. But during that violent creation, the raw materials vaporized and melted, he said.
The seven samples "are what it looked like before," he said. "They are quite lovely."
Scientists captured the interstellar dust, rather than other random debris, by orientation of the spacecraft. They know that interstellar dust passes through space in a specific direction much as driving snow hits the front, not rear, of a car windshield, said Scott Sandford, an astrophysicist at NASA's Ames Research Center in Moffett Field.
"These are the most challenging objects we will ever have in the lab for study, and it is a triumph that we have made as much progress in their analysis as we have," said Michael Zolensky, curator of the Stardust laboratory at NASA's Johnson Space Center in Houston and co-author of the Science paper. They are almost impossibly small, far too tiny to see with the naked eye. A trillion would fit in a teaspoon. To be studied, they must be viewed under a special X-ray microscope.
Scientists have been startled to discover that the particles aren't made of a single dense material, but are an agglomeration like a tossed salad of other particles, such as the olivine, magnesium-iron-silicate mineral.
More studies are needed to identify their age, their precise chemistry and their origins.
At Berkeley, they are sheltered in a special nitrogen-filled box, about the size of a large microwave, safely shielding them from oxygen and other contaminants.
The Stardust probe was launched in 1999 to meet a comet and capture some of its tailing materials. It returned to Earth in 2006 in a three-billion mile journey. An onboard canister held a tennis racket-like tray that captured particles as the spacecraft flew. One side of the tray holds traces of a comet; on the other, interstellar dust.
A team of scientists has been combing through the spacecraft's dust collectors.
The team was helped by "citizen scientists" around the world -- volunteers called "Dusters" in the Stardust@home project -- who searched the probe's detectors.
Until now, such stuff was viewed from afar, through telescopes. "We only knew the general properties of interstellar space," said Westphal.
"This is about our own origins -- understanding the stuff that made our solar system, our planet and us."
Contact Lisa M. Krieger at 650-492-4098.