With NASA's Stardust spacecraft due to drop its cosmic samples to Earth on 15 January, mission planners are trying to enlist thousands of internet users to help analyse its payload, in a project called Stardust@home.
Stardust was launched in 1999 with the principle aim of collecting dust from the trail of Comet Wild 2, which is thought to have remained nearly unchanged since its formation in the early solar system, about 4.5 billion years ago. But on its way to the comet, the spacecraft also captured interstellar dust by periodically exposing the "reverse" side of its sponge-like, aerogel collector to space.
This side may contain grains of dust from distant stars that spewed out material as they died – clues that could reveal the internal physics of these stars. But based on previous interstellar dust measurements by spacecraft such as Galileo, researchers expect Stardust scooped up just 45 grains of this dust in its tennis-racket-sized collector.
The team likens finding these tiny particles to tracking down 45 ants on a football field. So to ease the process, researchers decided to recruit the help of volunteers over the internet in a project broadly similar to SETI@home, which uses people's idle computers to search radio telescope data for signals from extraterrestrial life.
But Stardust@home will be much more interactive, as users will have to carefully scrutinise microscopic images of the aerogel for the carrot-shaped tracks left behind when the dust grains ploughed into the collector.
"Twenty or 30 years ago, we would have hired a small army of microscopists, who would be hunched over microscopes focusing up and down through the aerogel looking for the tracks," says team member Andrew Westphal of the University of California in Berkeley, US. "Instead, we developed an automated microscope to scan the aerogel and hope to use volunteers we have trained and tested to search for these tracks."
Each of the planned 1.5 million aerogel images will be scanned by four people – a task that would take at least 30,000 hours for a single person to do. Volunteers will be chosen after passing a test where they identify tracks in sample images.
If at least two people find a track in one of the real images, the image will be sent to 100 more volunteers. If 20 or more of this group also find a track, the image will be sent to trained college students to evaluate. If confirmed, the grain will be removed for study and the original discoverers will be allowed to name it.
A capsule containing Stardust's samples is scheduled to make a parachute landing in Utah, at 1012 GMT on 15 January. The Stardust@home project was announced on Tuesday at a meeting of the American Astronomical Society in Washington DC, US.
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10:45 10 October 2008
19:00 09 October 2008
