For the first time, scientists on Earth may have obtained dust particles from outside the solar system, thanks to a NASA spacecraft whose mission ended in 2006.

According to a press release from NASA's Jet Propulsion Laboratory (JPL), scientists had been examining material brought back on the Stardust spacecraft ever since it returned to Earth. Pending confirmation, these seven particles would be the first ever recovered from interstellar space.

One paper is published Friday in the journal Science and a dozen more are expected next week in the journal Meteoritics & Planetary Science.

"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," Michael Zolensky, co-author of the Science paper and curator of the Stardust laboratory at NASA's Johnson Space Center in Houston.

In a separate press release, from the University of California - Berkeley (UCB), study researchers said the particles have been literal needles in a haystack. Two of them are approximately two microns, which equates to thousandths of a millimeter.

Study lead author Andrew Westphal, a physicist at UCB's Space Sciences Laboratory, called the particles "very precious."

"The fact that the two largest fluffy particles have crystalline material - a magnesium-iron-silicate mineral called olivine - may imply that these are particles that came from the disks around other stars and were modified in the interstellar medium," he said in the release. "We seem to be getting our first glimpse of the surprising diversity of interstellar dust particles, which is impossible to explore through astronomical observations alone."

A physicist at UCB, Anna Butterworth is an author on one of the forthcoming papers.

"This dust is relatively new, since the lifetime of interstellar dust is only 50 to 100 million years, so we are sampling our contemporary galaxy," she said in the release. "We expected to find grains less than a micron across that would leave a track a couple of microns wide. That is about one-fiftieth the width of a human hair. We might not see the particles in an optical microscope, so the Dusters are looking for the impact tracks they made."