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Projects: Stardust@homeStardust@home Project Update: scanning Begins at JSCApril 26, 2006: The interstellar dust collector was one side of Stardust's tennis racquet-shaped aerogel collector, the other side being reserved for particles from comet Wild 2. On two occasions during its long 7-year voyage, from February to May of 2000, and again from August to December 2002, while passing between the orbits of Mars and Jupiter, Stardust crossed a stream of interstellar dust that flows into the solar system. The stream is composed of minute particles from distant stars, light years away, and its apparent motion is the result of the movement of our own solar system through the galaxy. As it passed through, Stardust extended its aerogel collector, exposing the side designed to collect interstellar dust. It didn't collect much. Even with several months of exposure, scientists believe that Stardust picked up no more than a few dozen miniscule particles, each no more than a micron or two in diameter. On January 15, 2006, Stardust's Sample Return Capsule parachuted gently onto the Utah desert carrying with it the precious samples of interstellar dust. Scientists are eager to study these exotic grains, the first particles from other suns ever brought to Earth from space. But before they can do so they must first locate them within the collector itself, and this, it turns out, is a daunting task. The particles are few and tiny, the collector large (1000 centimeters square), and the aerogel -- though seemingly clear and pristine -- is in fact cracked and flawed when scrutinized under a microscope. Locating interstellar dust grains in that environment makes finding a needle in a haystack seem easy. Nevertheless, it is precisely the task assigned to Stardust@home.
Around the middle of May, Stardust@home will begin sending out digital "movies" of each tiny section of the aerogel to volunteers worldwide. They will scan each movie using a web-based program called a "Virtual Microscope," and return the results to Stardust@home headquarters in Berkeley. Stardust@home team leaders believe that with the help of thousands of volunteers they will be able to complete this seemingly impossible task within a few months. The first stage, however, is to microscopically scan the entire surface of the aerogel collector. The images taken will then be used to create the 1.6 million "movies" that will be sent to Stardust@home volunteers. Anna's mission in going down to JSC was to set the scanning process in motion. On Friday, that's exactly what she did. Since January, when it was separated from its twin – Stardust's cometary particle collector – the interstellar dust collector had been stored at the Stardust lab in building 31 at the Johnson Space Center. Accompanied by Anna and his JSC colleagues Jack Warren, Ron Bastien, and Tom See, Stardust curator Mike Zolensky entered the lab and extracted the collector from its storage in a nitrogen-purged container. He then physically carried the collector on what can be described as the last stage of its 3 billion-mile journey – just down the hall to the newly established Stardust@home laboratory.
On most days, the room housing the Stardust@home laboratory is known as JSC's cosmic dust lab. For the next few months, however, it will serve exclusively as the scanning station for Stardust@home. Once the scanning is done, the microscope and other equipment will be dismantled, and the lab will revert to its former use. On entering the lab, Anna, Mike, and their companions donned the clean white suits designed to prevent any contamination of the samples. A constant stream of air blowing gently but steadily through the tunnel-shaped lab also helps keep the samples pristine: the scientists handling the collector always stand "downwind" from samples, thus ensuring that nothing blows from them onto the samples. Together, Mike, Jack , Ron and Anna removed the covers that had protected the interstellar dust collector for the last three months. They then placed the entire collector carefully on the microscope stage and secured it in place. The scanning was now ready to begin.
For the next three hours the scanning system seemed to work flawlessly. The microscope, operating automatically, focused on about 100 miniscule areas on the aerogel surface, producing 40 images with different focus-depths for each. Back in Berkeley, these will be used to produce the "movies" that will be sent out to Stardust@home volunteers. Then it was time to pack up for the weekend: the collector was removed from the microscope stage, and stored in a dry nitrogen-purged cabinet inside the Stardust@home lab. It will not leave the room until the scanning is completed. Anna returned to Berkeley on Saturday, carrying with her the data gathered on that first day of scanning. Together with Andrew Westphal, they will spend the next few days analyzing the results and making sure that the quality of the images is satisfactory. Back in Houston, the scanning itself will from now on be conducted by Mike Zolensky's JSC curatorial team. The Stardust@home scanning is now on track and will continue for the next several months. As soon as a sufficient number of movies is produced, they will begin sending the movies to Stardust@home volunteers for review. Anna's Houston mission had been accomplished. - Amir Alexander |
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