According to a Thursday announcement by NASA, the Stardust probe, which returned to Earth with samples of a comet, may also have picked up seven particles from interstellar space. These particles were likely hurtled into space by the explosion of a super nova millions of years ago and then altered by exposure to interstellar space. Scientists are still testing the particles to confirm their origins. If they are confirmed as interstellar dust, they may provide clues to the origins of the solar system.
Stardust was launched in 1999 and encountered Comet Wild-2 in 2002. It captured a sample of the comet in an aerogel container, as well as, apparently, interstellar dust. The container was separated from Stardust and returned to Earth in 2006. Meanwhile Stardust was renamed Stardust-NExT and encountered Comet Temple-1 in 2011. That comet was previously visited by the Deep Impact probe which launched an impactor against its surface. That would make Temple-1 the first comet to have been visited twice by two different space probes.
The particles vary in size, composition, and structure, seemingly to have different origins and histories. Two of the largest particles are described as fluffy and containing a magnesium-iron-silicate mineral. Some of the other particles contain sulfur, something scientists say should not occur in interstellar space.
Scientists also caution that the number of particles, even if they are confirmed to be interstellar in origin, would be too few to derive insights into the origin of the solar system. They do hold out hope that more interstellar dust particles might be discovered as the sample return canister is examined more thoroughly, though the expectation is that only a dozen or so interstellar particles will be found. The hope is that the discovery will lead to a new mission that is entire dedicated to capturing interstellar dust, collecting thousands of samples.