The minerals found in the particles suggest that the early solar system was a chaotic place where bits of material might be flung from the area near the sun to the solar system's furthest reaches, University of Washington astronomer and project lead scientist Donald Brownlee told the Associated Press.
The comet dust was collected by NASA's Stardust spacecraft, which launched in 1999 and crossed paths with the comet Wild 2 in 2004. A new type of material called an aerogel allowed the spacecraft to safely capture some of the speeding particles surrounding the fast-moving comet. A capsule containing the particles returned to earth in January, and scientists have been analyzing the comet dust ever since.
Scientists expected the particles to be made of interstellar dust from the cooler outer regions of the solar system, where the comets formed. Instead, they found that the dust also included a material, called a calcium-aluminum inclusion, forged in the hot inner solar system near the sun. That material then traveled out to the edge of the solar system beyond Pluto and coalesced with interstellar dust to form the comets.
"As the solar system formed 4.6 billion years ago, material moved from the innermost part to the outermost part. I think of it as the solar system partially turning itself inside out," Brownlee said in a press statement.
The results, he told the magazine New Scientist, "indicate that mixing on the grandest scales was possible in the early universe." Those results will be published Friday in the journal Science, and were presented today at the American Geophysical Union meeting in San Francisco.
Astronomer Don Burnett, of the California Institute of Technology, says that the results are a big step for comet research--and that there is still much more to be learned from the Stardust material.
The 200 researchers who have been analyzing the dust thus far have used only a small fraction of the several micrograms of material Stardust collected, he told New Scientist.
"This is not the end of the Stardust results. It is just the beginning," he said.
