A team of researchers including scientists from UC Berkeley and NASA Ames Research Center announced on Thursday that seven microscopic interstellar dust particles have been discovered among samples collected by NASA's Stardust spacecraft. Scientists have been studying the spacecraft's payload since its return to Earth in 2006. The dust motes probably came from beyond our solar system and may have been formed in a supernova explosion millions of years ago. If confirmed, these would be the first samples of contemporary interstellar dust.
“They are very precious particles,” said Andrew Westphal, a physicist at UC Berkeley’s Space Sciences Laboratory and the lead author, with 65 coauthors, of a report on the particles appearing in the Aug. 15 issue of the journal Science.Twelve other papers will be published next week in the journal Meteoritics and 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," said Michael Zolensky, curator of the Stardust laboratory at NASA’s Johnson Space Center in Houston and coauthor of the Science paper.
The Stardust spacecraft launched from Cape Canaveral Air Force Station in Florida on February, 1999. Its primary mission was to collect dust samples from comet Wild-2 as well as collecting samples of comic dust. Stardust used a collector tray containing 90 blocks of aerogel to trap the dust particles. aerogel is a silicon based solid with a porous structure that is 1,000 times less dense than glass. When Stardust made a fly-by of Earth in 2006, the spacecraft jettisoned its Sample Return Capsule (SRC) which made a parachute landing in Utah.
Two of the tiny particles were isolated from the aerogel after their impact tracks were detected by volunteers know as "Dusters" who participated in a UC Berkeley citizen science project called Stardust@home. The volunteers scanned millions of images in search of tiny impact tracks. Two of the Dusters where named as co-authors in the paper published in Science.
A third track was discovered but the tiny particle seems to have vaporized due to the great speed it was traveling when it hit the collector. An additional 100 tracks found by Dusters still need to be analyzed, and only 77 of the 132 aerogel tiles have been scanned for tracks. Four particles were discovered embedded in the aluminum foils between aerogel tiles. So far, only about 5% of the foils have been searched for particles.
The two aerogram-embedded particles, named Orion and Hylabrook by their discoverers will be subjected to further tests to determine their oxygen isotopes abundances which could provide further evidence that they are interstellar in origin. Stardust@home will continue to analyze the remaining aerogel tiles and foil analysis will soon be added to the project.