[meteorite-list] Stanford Examines Comet Particles
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Feb 6 14:24:32 2006 Message-ID: <200602061922.k16JMqW23014_at_zagami.jpl.nasa.gov> http://daily.stanford.edu/tempo?page=content&id=19254&repository=0001_article Stanford examines comet By Kat Lewin The Stanford Daily February 6, 2006 Scientists at Stanford have been feeling a little spacey lately. On Jan. 15, NASA's Stardust mission touched down after a seven-year excursion through space, bearing precious interstellar dust. The particles brought back are now being evaluated at approximately two-dozen universities, including Stanford as part of project Stardust_at_home. The stardust was collected from the tail of comet WILD-2 (pronounced "vilt"). According to Sean Brennan, a physicist at the Stanford Synchrotron Radiation Laboratory (SSRL) physicist, this collection was especially significant because the comet has only passed by the sun five times. "This is the first time we have brought back extraterrestrial materials since Apollo, and it's the first time we've had access to pristine meteoric material," Brennan said. "Prior to '74, WILD-2 was in orbit outside of Jupiter, far from the sun. We were worried that everything we'd been looking at had been processed by the sun. What you really want to do is fly out past Jupiter and grab one of those rocks." The limited exposure to the sun differentiates the particles from meteorites that have been studied in the past, explained third-year chemistry graduate student Maegan Spencer, who will also be studying the space dust. "When a meteorite falls to Earth it's so hot it forms a fusion crust," Spencer said. "The rock melts and preserves everything in it." Spencer and Brennan are both part of collaborative preliminary examination team comprised of about 150 scientists all over the world, Spencer explained. This team will have exclusive access to the particles until September 2006, according to Brennan, and will analyze aspects of the dust ranging from bulk chemistry to isotopes to amino acids and organic compounds. Among the first institutions to have access to these particles are a BayPac consortium of approximately 15 to 20 scientists from the Stanford Linear Accelerator Center (SLAC), UC-Berkeley and the Lawrence Livermore National Laboratory. The team's results will be published collectively until the end of this time period, after which the particles will be made available to other members of the scientific community. "In science there's this unfortunate reputation of competition," Brennan said. "People may ask: Why did Berkeley get the samples before us? But in the end, we're trying to get the best science out there." To this end, scientists have been developing methods to retrieve and examine the particles since the project's launch. A major obstacle confronted by the mission, according to Spencer, was figuring out how to collect the samples slowly enough that they were not damaged. To accomplish this, the collection plate on the shuttle was fitted out with 130 panels of a substance called aerogel. Aerogel is a silica structure, like glass, that is 99.9 percent air, making it the lowest density solid known to man, Spencer said. Due to this, it has been dubbed "solid smoke." The low density of the aerogel allowed the particles to be slowly captured by the shuttle. "The comet moves at six times the speed of a rifle bullet," Spencer said. "Usually you can't see the particles with the naked eye, so scientists study the tracks and trails the dust leaves in aerogel. When particles go through aerogel, they leave fragmentary debris." Spencer will analyze this debris through two-step laser mass spectrometry in order to find polycyclic aromatic hydrocarbons. She is part of a team of scientists studying the organics of the particles based on these fragments left in aerogel. "We can get information out of stuff that would be trash to other people," she said. Brennan and his research partners, Konstantin Ignatyev, Katharina Luening and Piero Pinanetta will map the elemental composition of the particles using an X-ray microprobe at SLAC. According to Brennan, this will help scientists begin to evaluate the process of star formation. "This is a piece of unaltered pre-solar material," Brennan said. "Our solar system coalesced out of pre-solar nebula 4.6 billion years ago. Think about it: you have all this dust, and the lion's share becomes the sun, the next biggest portion forms Jupiter, and the rest is left for the other planets - but there's still some floating around, and it makes comets. WILD-2 is one of those comets. This is an extremely important step forward in potentially improving our understanding of how the solar system was formed." Brennan's team is slated to start research at the end of February; analysis of the particles has already begun for some members of the BayPac consortium. "We are not going to have completely studied these particles by the end of our allotted time," Brennan said. "We will be examining them for five years minimum before we run of out tests to do on them. This is going to be a treasure trove for years to come." Received on Mon 06 Feb 2006 02:22:51 PM PST |
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