evolutionary transubstantiation
The first analysis of space dust collected by a special collector onboard NASA’s Stardust mission and sent back to Earth for study in 2006 suggests the tiny specks, which likely originated from beyond our solar system, are more complex in composition and structure than previously imagined.
The analysis, completed at a number of facilities including the U.S. Dept. of Energy (DOE)’s Lawrence Berkeley National Lab (Berkeley Lab) opens a door to studying the origins of the solar system and possibly the origin of life itself.
“Fundamentally, the solar system and everything in it was ultimately derived from a cloud of interstellar gas and dust,” says Andrew Westphal, physicist at the Univ. of California, Berkeley’s Space Sciences Laboratory and lead author on the paper published this week in Science. “We’re looking at material that’s very similar to what made our solar system.”
Scientists believe that seven tiny grains of dust collected by NASA's Stardust mission could be the first ever such particles discovered that originated in interstellar space and traveled to our solar system
Westphal, who is also affiliated with Berkeley Lab’s Advanced Light Source, a DOE Office of Science User Facility where some of the research was conducted, and his 61 co-authors found and analyzed a total of seven grains of possible interstellar dust and presented preliminary findings. All analysis was non-destructive, meaning that it preserved the structural and chemical properties of the particles. While the samples are suspected to be from beyond the solar system, he says, potential confirmation of their origin must come from subsequent tests that will ultimately destroy some of the particles.
“Despite all the work we’ve done, we have limited the analyses on purpose,” Westphal explains. “These particles are so precious. We have to think very carefully about what we do with each particle.”
Between 2000 and 2002, the Stardust spacecraft, on its way to meet a comet named Wild 2, exposed the special collector to the stream of dust coming from outside our solar system. The mission objectives were to catch particles from both the comet coma as well as from the interstellar dust stream. When both collections were complete, Stardust launched its sample capsule back to earth where it landed in northwestern Utah. The analyses of Stardust’s cometary sample have been widely published in recent years, and the comet portion of the mission has been considered a success.
Milky Way at 10,000 feet—Mt. Crested Butte, Colorado
This new analysis is the first time researchers have looked at the microscopic particles collected en route to the comet. Both types of dust were captured by the spacecraft’s sample-collection trays, made of an airy material called aerogel separated by aluminum foil. Three of the space-dust particles (a tenth the size of comet dust) either lodged or vaporized within the aerogel while four others produced pits in the aluminum foil leaving a rim residue that fit the profile of interstellar dust.
“Almost everything we’ve known about interstellar dust has previously come from astronomical observations—either ground-based or space-based telescopes,” says Westphal. But telescopes don’t tell you about the diversity or complexity of interstellar dust, he says. “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.”
The researchers found that the two larger dust particles from the aerogel have a fluffy composition, similar to that of a snowflake, says Westphal. Models of interstellar dust particles had suggested a single, dense particle, so the lighter structure was unexpected. They also contain crystalline material called olivine, a mineral made of magnesium, iron, and silicon, which suggest the particles came from disks or outflows from other stars and were modified in the interstellar medium
Three of the particles found in the aluminum foil were also complex, and contain sulfur compounds, which some astronomers believe should not occur in interstellar dust particles. Study of further foil-embedded particles could help explain the discrepancy.
