By Helen Briggs
BBC News science reporter
Members of the public are being asked to help study cosmic dust samples returned by the Stardust space mission.
Stardust has captured primeval dust
A capsule containing dust from stars light years away landed in the Utah desert on Sunday.
The particles are buried in gel that was exposed to the interstellar dust stream during the probe's seven-year voyage around the Solar System.
Scientists need volunteers to sift through millions of pictures of the gel to locate the few dozen tiny grains.
The project, known as Stardust@home, has been set up by researchers at the University of California, Berkeley.
"No-one has ever had a contemporary interstellar dust particle in the lab, ever, to study," senior fellow Andrew Westphal told the BBC News website. "It is really a unique opportunity."
Dr Westphal developed the technique that the US space agency (Nasa) will use to scan the ultra-light gel (aerogel) in which the interstellar dust grains are embedded.
The gel - which is contained within a "honeycomb" of collector trays - will be scanned by an automated microscope at a clean room in Nasa's Johnston Space Center in Houston shortly after landing.
The aerogel is contained within collector trays
The impacts are almost invisible and can only be found with a microscope with a field of view smaller than a grain of salt.
Volunteers will be able to access the images via a web-based "virtual microscope". To take part, they need a reasonably up-to-date computer with Netscape or Internet Explorer, patience and some spare time.
People who register will have to go through a web-based training session to see if they are suitable. Dr Westphal believes the untrained eye may be better at spotting what amounts to a cosmic needle in a haystack.
"It's probably better for people to look who won't have any pre-conceived notion of what these things look like," said Dr Westphal.
Scientists think they will find only a few dozen interstellar grains. More than 1.6 million individual fields of view will have to be searched over the course of several months.
Once located, the particles will be extracted from the gel and analysed in research labs around the world.
A simulation of particles hitting aerogel
"We will probably find the first grain within the first month," Dr Westphal said.
As well as the satisfaction of taking part in the space project, volunteers have another incentive - the chance to name any dust grains they find.
"There is a tradition in the interplanetary dust community that people name particles, usually those collected in the stratosphere by high flying aircraft," said Dr Westphal.
Examples to date included Florian and Benavente, he added.
Stardust's main mission was to chase a comet and capture material from its coma, the cloud of dust and gas that surrounds its nucleus.
But it also trapped a sprinkling of dust from the interstellar stream that flows through the Solar System.
The particles contain the heavy chemical elements that originated in stars.
"Ultimately, this is the stuff we are made of," said Dr Westphal.
"The fact that we really don't know what the typical interstellar grain looks like is outrageous - this is really a search for our own origins."