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Stardust reveals surprising anatomy of a comet NASA/JPL NEWS RELEASE Posted: June 17, 2004 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.
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.
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.
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Scientist present new findings from the Stardust spacecraft's encounter with Comet Wild 2 in this news conference from NASA Headquarters on June 17. (26min 12sec file)
New pictures of Comet Wild 2 from NASA's Stardust spacecraft are shown here with narration by lead mission scientist Donald Brownlee. (3min 06sec file)
Animation depicting Stardust's flyby of Comet Wild 2 and the powerful jets of dust streaming from the comet's surface is presented with narration by scientist Benton Clark. (1min 59sec file)
After releasing its report, the President's Commission on Moon, Mars and Beyond holds a news conference in Washington. (60min 18sec file)
NASA Administrator Sean O'Keefe and commission chairman Pete Aldridge address the NASA workforce and answer questions after the Moon, Mars and Beyond report is released. (75min 24sec file)
Mars rover Spirit's arrival at the Columbia Hills, trouble with one of its wheels and Opportunity's descent into Endurance Crater and all of the latest pictures are presented at this briefing from June 15. (30min 27sec file)
Cameras on Opportunity provides this "ride-along" view of the rover's risky drive into Endurance Crater. Expert narration by science team member Scott McLennan. (30sec file)
Another stunning color panorama from the Mars rover Opportunity looking into Endurance Crater and the surrounding plains is presented with expert narration by science team member Scott McLennan. (1min 30sec file)
Spirit has generated this panorama from the base of the Columbia Hills. Expert narration is provided by science team member Larry Soderblom. (1min 15sec file)
New pictures from Mars rover Spirit showing the "Pot of Gold" rock area and other features are revealed with expert narration by science team member Larry Soderblom. (4min 47sec file)
