Stardust@home: Searching for Cosmic Needles in a Haystack

The Planetary Society, the founding sponsor of SETI@home, is again teaming with the University of California at Berkeley to engage the public in real science. The new project – Stardust@home – will allow internet users to help researchers search for microscopic interstellar dust particles captured by NASA's Stardust spacecraft, scheduled to return its fragile cargo to Earth on January 15, 2006.

Like cosmic needles in a haystack, only a few dozen particles will be scattered through the collection medium of aerogel, a spongy material that is the lightest known manmade substance. Stardust’s primary mission was to return dust particles captured from comet Wild 2 when it passed through the comet’s coma in January 2004. But while cruising through space on its way to the dramatic encounter with Wild 2, the spacecraft was also designed to use the back side of its aerogel collector to capture stardust from distant suns.

“Think of the dust particles as bugs smashing into a really soft windshield,” said Bruce Betts, The Planetary Society’s Director of Projects. “On long trips, you expect to collide with a few bugs as you cruise down the highway, but in this case, you want to collect them intact, without smooshing, or vaporizing, them.”

Andrew Westphal, a UC Berkeley senior fellow and associate director of the campus' Space Sciences Laboratory, developed the technique NASA will use to digitally scan the aerogel in which the interstellar dust grains are embedded. The team expects to find approximately 45 grains of microscopic dust embedded in the aerogel collector. Spotting these few and minute particles within the aerogel, scarred and cracked from 7 years in space, is no simple matter. In fact, when NASA launched Stardust seven years ago, scientists had no idea how the task would be accomplished. To resolve the problem, Westphal and his team took a page from the phenomenal success of SETI@home and called in the public’s help. And that’s where Stardust@home comes in.

Just as SETI@home was a wildly successful distributed computing program that brought together millions in a search for extraterrestrial intelligence, Stardust@home will draw together users from around the world to search for tiny grains of interstellar dust. And once again The Planetary Society will help recruit the volunteers needed.

After the Stardust samples return to Earth, Westphal and his team at UC Berkeley's Space Sciences Laboratory will take 1.6 million “movies” of the aerogel collector, each covering a different minute portion. Each movie focuses on 60 different depths within the aerogel, from a little above the surface to a depth of 100 microns. Each user will receive a movie to watch to look for interstellar grains with the aid of an online “virtual microscope.” Once a volunteer’s search is complete, Stardust@home will collect the results and send the user a new movie to view. Anyone on the internet can sign up with Stardust@home to help scan the aerogel for tracks left by speeding grains of interstellar dust. Each picture will cover an area smaller than a grain of salt.

Because no one knows exactly what these dust tracks will look like, the human eye – and good old-fashioned human intelligence – will be better at spotting them than a computer program. The public can begin signing up with Stardust@home in mid-March.

Unlike SETI@home, where one’s computer processed all the data, Stardust@home will be a hands-on activity. Each volunteer scanner will need to pass a test by spotting tracks made in test samples. The team will also keep scanners vigilant by occasionally throwing into the mix a “ringer” – an artificially made track – to see if it is found.

If at least two out of four volunteers viewing each image report a track, that image will be fed to 100 more volunteers for verification. If at least 20 of these report a track, UC Berkeley undergraduates expert at spotting dust grain tracks will confirm the identification Eventually the grain will be extracted for analysis. Discoverers will have the chance to help name the dust grains that they find.

In addition to helping recruit Stardust@home volunteers, The Planetary Society will also offer on its website extensive background information on both the Stardust mission and the science of interstellar dust.

The Society has a second connection with the Stardust mission. The names of all its members around the world at the time of launch are included on a microchip on the spacecraft, the first such collection of names from the public to have made a round trip to space and back.

On January 15, 2006, Stardust will swing by Earth once more and release a sample return capsule, which will parachute down onto the Utah desert. Nestled within the capsule’s science canister will be the two sets of samples: cometary particles on one side of the aerogel collector, and interstellar dust on the other.

What might we learn from these first interstellar dust particles collected outside our planet’s atmosphere? Scientists hope they will reveal more about the internal processes of supernovas, red giants, or neutron stars that produce not only interstellar dust but also generate the heavy elements like carbon, nitrogen, and oxygen necessary for life.

The virtual microscope was developed by computer scientist David Anderson, the director of the SETI@home project, along with physics graduate student Joshua Von Korff.