In the first analysis of space dust sent to earth by NASA's Stardust mission, physicists suggest that the tiny specks, which likely originated from beyond our solar system, are more complex in composition and structure than previously imagined.
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.
Stardust launched its sample capsule back to earth where it landed in northwestern Utah.
In the new analysis, researchers 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 aluminium foil.
Three of the space-dust particles either lodged or vaporised within the aerogel while four others produced pits in the aluminium foil leaving a rim residue that fit the profile of interstellar dust.
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Researchers used the scanning transmission x-ray and Fourier transform infrared microscopes at the Advanced Light Source (ALS) at Berkeley Lab.
They found that the two larger dust particles from the aerogel have a fluffy composition, similar to that of a snowflake.
Three of the particles found in the aluminium foil were also complex, and contain sulfur compounds, which some astronomers believe should not occur in interstellar dust particles.
"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," said Andrew Westphal, a physicist at the University of California, Berkeley's space sciences laboratory.
The analysis opens a door for the study of the origin of the solar system and possibly the origin of life itself.
The paper was published in the journal Science.