August 15, 2014
Analysis Of Stardust Mission Particles Reveals First Potential Interstellar Space Dust
redOrbit Staff & Wire Reports - Your Universe Online
Seven rare and microscopic particles of space dust collected by instruments onboard NASA’s Stardust mission could be the first samples of contemporary interstellar dust ever obtained by scientists, an international team of researchers report in Friday’s edition of the journal Science.
The samples, which were gathered by Stardust’s aerogel and aluminum foil dust collectors, likely originated from outside of our solar system. The authors believe the particles could have been created by a supernova explosion millions of years ago, and were then altered after being exposed to the extreme conditions of their environment.
Scientists have been analyzing the space dust particles since they first arrived on Earth in 2006, and they have discovered that they have a far more complex structure and composition than previously thought possible. In addition to the new Science study, several other papers detailing the research are currently scheduled to appear 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,” explained Michael Zolensky, co-author of the Science paper and curator of the Stardust laboratory at the NASA Johnson Space Center in Houston.
“Fundamentally, the solar system and everything in it was ultimately derived from a cloud of interstellar gas and dust,” added lead author Andrew Westphal, physicist at the University of California, Berkeley's Space Sciences Laboratory. “We’re looking at material that's very similar to what made our solar system.”
Stardust was launched in 1999 and returned to Earth in January 2006, and once it arrived back on the planet, its sample return canister was transported to Zolensky’s facility at Johnson, where they were preserved and protected for noninvasive research. The analysis was conducted at multiple facilities, including the Lawrence Berkeley National Lab in California, and emphasized preserving the structural and chemical properties of the particles.
While the astronomers believe the dust samples originated from beyond our solar system, that cannot be confirmed until tests are conducted that will ultimately destroy some of the particles. Thus far, though, Westphal said that they have “limited the analyses on purpose” due to the “precious” nature of the samples. He added that they are taking the time “to think very carefully about what we do with each particle.”
The scientists report that the particles are far more diverse chemically and structurally than they had expected, as the smaller ones differ greatly from the larger ones and appear to have a different history. Many of the larger ones were described as being fluffy and resembling a snowflake, they noted.
Two of the particles, each about two microns (thousandths of a millimeter) in diameter, were isolated from the others after a team of citizen scientists discovered their tracks. Those individuals scanned over one million images as part of a volunteer project at the University of California, Berkeley. A third track was left behind by a particle that appeared to be moving more than 10 miles per second – so fast that it wound up vaporizing, according to NASA.
Four particles featured in the Science study were discovered in aluminum foils between tiles on the collector tray, the US space agency added. While those foils were not designed to serve as dust collection surfaces, Rhonda Stroud of the Naval Research Laboratory and her colleagues searched them, identifying a quartet of pits that were lined with material comprised of elements said to fit the profile of interstellar dust particles.
Three of those four particles contained sulfur compounds, which some experts claim is not found in particles of interstellar dust. NASA said that a preliminary examination team plans to continue analyzing the remaining 95 percent of the foils, hoping to discover enough particles to understand the variety and origins of interstellar dust.
“Almost everything we've known about interstellar dust has previously come from astronomical observations – either ground-based or space-based telescopes,” said Westphal. “The analysis of these particles captured by Stardust is our first glimpse into the complexity of interstellar dust, and the surprise is that each of the particles are quite different from each other.”
Image 2 (below): The largest interstellar dust track found in the Stardust aerogel collectors was this 35 micron-long hole produced by a 3 picogram speck of dust that was probably traveling so fast that it vaporized upon impact. The other two likely interstellar dust grains were traveling more slowly and remained intact after a soft landing in the aerogel. Credit: Andrew Westphal, UC Berkeley
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