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diff --git a/13082-0.txt b/13082-0.txt new file mode 100644 index 0000000..e1bea1f --- /dev/null +++ b/13082-0.txt @@ -0,0 +1,124 @@ +*** START OF THE PROJECT GUTENBERG EBOOK 13082 *** + +Thanks to David Reed for sending us these files. + + + +NASA Spacecraft Reveals Surprising Anatomy Of A Comet +06.17.04 + +Findings from a historic encounter between NASA's Stardust +spacecraft and a comet have revealed a much stranger world +than previously believed. The comet's rigid surface, dotted +with towering pinnacles, plunging craters, steep cliffs, and +dozens of jets spewing violently, has surprised scientists. + +Image above: This image and diagram show the comet Wild 2, +which NASA's Stardust spacecraft flew by on Jan. 2, 2004. The +picture on the left is the closest short exposure of the +comet. The listed names on the right are those used by the +Stardust team to identify features. "Basin" does not imply an +impact origin. + +Animation: This movie strings together a series of still +images of comet Wild 2 taken during Stardust's historic flyby +of the comet. Animation credit: NASA/JPL-Caltech. + +"We thought Comet Wild 2 would be like a dirty, black, fluffy +snowball," said Stardust Principal Investigator Dr. Donald +Brownlee of the University of Washington, Seattle. "Instead, +it was mind-boggling to see the diverse landscape in the first +pictures from Stardust, including spires, pits and craters, +which must be supported by a cohesive surface." + +Stardust gathered the images on Jan. 2, 2004, when it flew 236 +kilometers (about 147 miles) from Wild 2. The flyby yielded +the most detailed, high-resolution comet images ever. + +"We know Wild 2 has features sculpted by many processes. It +may turn out to be typical of other comets, but it is unlike +any other type of solar system body," Brownlee said. He is +lead author of one of four Stardust papers appearing in the +Fri., June 18, issue of Science. "We're fortunate that nature +gave us such a rich object to study." + +Stardust images show pinnacles 100 meters tall (328 feet), and +craters more than 150 meters deep (492 feet). Some craters +have a round central pit surrounded by ragged, ejected +material, while others have a flat floor and straight sides. +The diameter of one large crater, called Left Foot, is one +fifth of the surface of the comet. Left Foot is one kilometer +(.62 miles) across, while the entire comet is only five +kilometers (3.1 miles) across. + +"Another big surprise was the abundance and behavior of jets +of particles shooting up from the comet's surface. We expected +a couple of jets, but saw more than two dozen in the brief +flyby," said Dr. Benton Clark, chief scientist of space +exploration systems, Lockheed Martin Space Systems, Denver. + +The team predicted the jets would shoot up for a short +distance, and then be dispersed into a halo around Wild 2. +Instead, some super-speedy jets remained intact, like blasts +of water from a powerful garden hose. This phenomenon created +quite a wild ride for Stardust during the encounter. + +"Stardust was absolutely pummeled. It flew through three huge +jets that bombarded the spacecraft with about a million +particles per second," said Thomas Duxbury, Stardust project +manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. +Twelve particles, some larger than a bullet, penetrated the +top layer of the spacecraft's protective shield. + +The violent jets may form when the Sun shines on icy areas +near or just below the comet's surface. The solid ice becomes +a gas without going through a liquid phase. Escaping into the +vacuum of space, the jets blast out at hundreds of kilometers +per hour. + +The Stardust team theorizes sublimation and object hits may +have created the comet's distinct features. Some features may +have formed billions of years ago, when life began on Earth, +Brownlee said. Particles collected by Stardust during the Wild +2 encounter may help unscramble the secrets of how the solar +system formed. + +Stardust was launched in 1999. It is zooming back to Earth +with thousands of captured particles tucked inside a capsule. +The capsule will make a soft landing in the Utah desert in +January 2006. The samples will be analyzed at the planetary +material curatorial facility at NASA's Johnson Space Center, +Houston. + +Comets have been objects of fascination through the ages. Many +scientists believe they delivered carbon and water, life's +building blocks, to Earth. Yet their destructive potential is +illustrated by the widely held theory that a comet or asteroid +wiped out the dinosaurs. + +To view Stardust images on the Internet, visit: +http://stardust.jpl.nasa.gov or +http://photojournal.jpl.nasa.gov/ + + + + + + + + + Equal Employment Opportunity Data Posted Pursuant to the No Fear + Act + + FY 2005 Budget Request + + 2003 Strategic Plan + + Freedom of Information Act + + The President's Management Agenda + + FY 2003 Agency Performance and Accountability Report + + NASA Privacy Statement, Disclaimer, + and Accessibility Certification + + Editor: Susan Watanabe + NASA Official: Brian Dunbar + Last Updated: June 28, 2004 + + Contact NASA + +*** END OF THE PROJECT GUTENBERG EBOOK 13082 *** |