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" I&amp;#039;m in the cockpit of a modified DC-8 cruising 39,000 ft. above Nevada in the early hours of Jan. 15, 2006. The plane, which is owned by NASA and operated jointly with the University of North Dakota, is on an intercept course with the fastest man-made object ever to enter Earth&amp;#039;s atmosphere\u2014the Stardust spacecraft&amp;#039;s 101-pound Sample Return Capsule (SRC), which is heading home at meteoric speed after a seven-year, 2.9 billion-mile journey. Over the headset I can hear excitement\u2014and tension\u2014in the voices of the scientists in the cabin as they check their equipment. They are getting ready for a long-awaited opportunity to collect data on the SRC&amp;#039;s re-entry shock wave, and heat and light signatures, which they hope will reveal how comets may have brought the building blocks of life to Earth. It&amp;#039;s going to hit us! That&amp;#039;s my first thought when I see a bluish white object 50 times brighter than any star blaze across the clear winter night. It&amp;#039;s the SRC, and it seems to be heading straight for the plane. It&amp;#039;s moving at the heart-stopping rate of nearly 29,000 mph; that&amp;#039;s 8 miles per second, or 10 times faster than a rifle bullet. Pilot Frank Batteas is too busy holding his course to look out the window at the spectacular fireball trailing a gray tail of smoke. So, I lean forward in my jumpseat and tap him on the shoulder to get his attention. Batteas turns; his eyes open wide as he sees the white-hot capsule. Although the SRC looks close enough to brush the nose of the plane, it&amp;#039;s actually 40 miles away, moving left to right, speeding to its landing zone in the U.S. Air Force&amp;#039;s Utah Test and Training Range southwest of Salt Lake City. After less than 30 seconds, the capsule flashes out of sight. Cheers fill the cabin. Down on the muddy ground of the test range, a second team of scientists is still waiting for a successful completion of the mission. Will the SRC&amp;#039;s new heat shield work? Will the parachute deploy, or will the SRC end up like the Genesis probe, which crashed in 2004 when its parachute failed to deploy, scattering a payload gathered during three years in space across the desert floor? For the Stardust team, a decade of research and $212 million are at stake. In the cockpit, we listen to the anxious communications between mission control and the helicopter recovery pilots who are scanning the nighttime desert for the deployed parachute. Twelve minutes later, a chopper pilot radios that they&amp;#039;ve found the parachute\u2014and the intact capsule beneath it. As technicians on the ground collect the SRC and take it to a clean room at the test range, the DC-8 heads back to NASA Ames Research Center in Mountain View, Calif. SEARCH FOR LIFE The Stardust spacecraft was launched on Feb. 7, 1999, from Cape Canaveral on a mission to gather star dust\u2014literally\u2014and to collect the first particles from a comet in space, Wild 2. The ultimate goal: to expand our understanding of our solar system and life on Earth. Pronounced &amp;quot;vilt 2&amp;quot; and named after Swiss astronomer Paul Wild who discovered it in 1978, the comet is believed to contain organic compounds nearly 4.6 billion years old, predating our solar system. &amp;quot;The atoms in our bodies were actually in star dust before the solar system was formed,&amp;quot; says Donald Brownlee, Stardust principal investigator and astronomy professor at the University of Washington, Seattle. &amp;quot;It is believed that the water, carbon and organic matter on Earth came from the outer solar system.&amp;quot; A year into the flight, the spacecraft opened the clamshell-like SRC for the first time, and then extended a 2 1/2-ft.-long aluminum collector shaped like a tennis racket. For 69 days the collector remained in position, gathering tiny particles while traveling at up to 12 1/2 miles per second. After a nearly two-year loop around the sun, the spacecraft swung by Earth to boost its speed enough to put it on an orbit that would intercept Wild 2 between Mars and Jupiter. During this second of three trips around the sun, the SRC opened again and spent four months capturing interstellar dust. During its third loop, Stardust met the comet. When it comes to collecting high-speed space dust, the biggest challenge is slowing the particles without altering their shape and chemical composition\u2014or vaporizing them entirely. The solution: a remarkable substance called aerogel, housed in back-to-back collector trays, each with 132 cells. When a speeding particle hits a collector cell, it buries itself in the extremely light, gelatin-like aerogel, creating a track up to 200 times its own length as it comes to a gradual stop. STORMY ENCOUNTER Five years into its mission, as Stardust closed in on Wild 2, it rotated so that its protective shields deflected the comet&amp;#039;s swirl of dust, gas and debris away from the spacecraft. The collector was extended again, this time with a fresh tray of cells on its other side exposed to gather cometary dust. On Jan. 2, 2004, disaster nearly struck. Stardust was hit three times by grape-size comet particles that penetrated three layers of protective Kevlar and struck the main structure. &amp;quot;We think that came close to destroying the spacecraft,&amp;quot; says project manager Tom Duxbury. Stardust continued on its mission, collecting thousands of cometary samples and transmitting 72 images to Earth as it passed within 155 miles of Wild 2. The surface of the comet appeared in unprecedented detail, showing 20 jets spewing cometary dust and rocks into space. Tucking the collector into the SRC, Stardust headed back toward Earth. HOME AT LAST Two years after its encounter with Wild 2, Stardust jettisoned the SRC and continued in its orbit around the sun. As the capsule hurtled toward Earth, it faced another technical challenge: A new type of heat shield had to withstand superheated gases and temperatures predicted to reach 5000 F, generated by the capsule&amp;#039;s hypersonic re-entry. Invented by NASA scientists Dan Rasky and Huy Tran, the shield was made of material called Phenolic Impregnated Carbon Ablator, or PICA. &amp;quot;A high-density version has been used for a long time, mostly on military vehicles,&amp;quot; Rasky says. The SRC version was of much lower density and lighter; the one-piece panel that covered half the capsule was just 2.25 in. thick. When Stardust was launched, the heat shield was brown. After re-entry it was the color of a charcoal briquette; pieces flaked off in scientists&amp;#039; hands. But early results indicate the PICA performed well. &amp;quot;It could be the heat shield for the Crew Exploration Vehicle,&amp;quot; Rasky says, referring to a key component in the space shuttle&amp;#039;s eventual replacement. THE RECKONING The SRC&amp;#039;s canister containing the samples was delivered to scientists at Johnson Space Center in Houston. &amp;quot;There was a level of fear that the particles had exploded on impact,&amp;quot; Brownlee says. He and Michael Zolensky, co-investigator for the Stardust mission, gingerly opened the canister and examined the first collector tray. &amp;quot;It was perfect,&amp;quot; Zolensky says. &amp;quot;It was so clean that for a second both Don and I thought, &amp;#039;Oh my gosh, it didn&amp;#039;t work\u2014it didn&amp;#039;t open in space.&amp;#039;&amp;quot; Upon closer inspection, however, it became clear that the collection system had worked flawlessly. The aerogel was intact, and the size and number of visible impacts in it exceeded all expectations. The grains were black, composed of organics, iron sulfides and iron magnesium silicates. &amp;quot;We were looking not only at the dawn of our solar system, but beyond that\u2014before there was a solar system,&amp;quot; Zolensky says. As Brownlee flashed a victory sign, his fellow scientists huddled around the collector&amp;#039;s aluminum grid, peering at the remains of ancient stars. "^^<http://www.w3.org/2001/XMLSchema#string>
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