BioEd Online

Just days after its official launch, the Stardust@home project has already run into a slew of problems: bizarre wedding snaps replaced microscope slides, the server went down and now there are accusations of cheating. But the project, which asks volunteers to search images for interstellar particles, seems well organized and could produce results in a few months' time.

In January this year, the spacecraft Stardust landed in the Utah desert. It had spent seven years collecting space dust in foam-like sheets of aerogel, and its cargo included matter from the comet Wild 2.

Researchers have already started to analyse the aerogel containing comet particles (see ' A comet's tale'). But another part of the aerogel, which was exposed to 'empty' space, presents a problem: finding the few dozen, minuscule grains of interstellar dust expected to be in this part of the gel is too difficult for a computer programme. So the scientists have turned to volunteers.

Cry for help

Researchers at the University of California, Berkeley, used an automatic scanning microscope to take more than 1.6 million images of the aerogel. On 1 August, they made a first batch of these pictures available over the Internet to anyone who cares to trawl through them. Viewers use the 'virtual microscope' to play through images of the aerogel at different focal depths.

Volunteers are asked to go through a training programme before registration to learn how to spot the telltale signs of a dust grain (a carrot-shaped hole), and to flag up anything they find. The scientific team then double checks those parts of the gel. A few lucky searchers could hope to find (and name) their own interstellar dust particle.

But things haven't gone smoothly. On its first day, the website shut down due to heavy traffic. And a few hours after re-opening, it had a stranger problem.

In among the speckled grey aerogel pictures appeared photos of weddings, bike riders, sunbathers and more. As the Stardust team put it: "Random images of unknown origin appear in the focus movies. We do not yet understand their origin, but they are not images of the Stardust Interstellar Dust Collector." Amused volunteers speculated about hackers, mischievous team members or problems with the server.

The project was back on track the next day, but no explanation was given.

Playing games

Glitches aside, there is another disadvantage to the volunteer-based project: some users seem to be more obsessed with getting a 'top score' than with finding anything real.

The system randomly checks volunteers' efforts by occasionally throwing in a 'test' photo, where the Stardust team already knows there is or isn't a sign of a dust particle. The volunteer's performance on these gives them a skill rating, which determines how seriously a claim to find a real dust particle is taken.

As was quickly documented on the website's forums, however, it is easy to cheat by simply looking carefully at the URL associated with each picture in order to distinguish 'test' pictures from the real ones that have yet to be analysed. Some users have cracked the trick admirably, boosting their skill ratings astronomically in a short period of time.

These users get name-checked on the site as skilled users, but they won't necessarily up their chances of finding a real grain or getting the credit for it. An aerogel image with a suspected dust particle must be positively identified by many volunteers, and by the scientists themselves. Although it is unclear who will ultimately get credit for being first to find a grain, a high skill ranking shouldn't affect this.

What are you looking at?

What might prove more problematic is the fact that no one has actually seen an interstellar dust particle embedded in Stardust's aerogel. There are precedents from other, similar projects, but no one knows exactly what a particle will look like.

Judging by the user forums, Stardust@home has generated real excitement, with many people commenting on the thrill of the search and wondering what to call the first interstellar particle they find.

The first explosion of interest (some 115,000 users signed up before the site opened) may die down, but there is no denying that by searching through a set of speckled grey aerogel images, you are actively participating in live space research. Have a go: it is surprisingly addictive.

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