NASA's audacious Stardust mission, a seven-year effort to learn more about the origins of the solar system by capturing particles from the tail of a comet and returning them to Earth, ended successfully Sunday when the spacecraft's scorched capsule parachuted into the Utah desert, its cargo intact.
The desk-sized capsule glowed red as it streaked across the sky over the northwest United States on its way to a 2:10 a.m. soft landing at the Air Force Test and Training Range in Dugway, Utah.
The mission was a major accomplishment for NASA's Jet Propulsion Laboratory in La Canada Flintridge and Lockheed Martin Space Systems in Denver, which jointly oversaw the spacecraft on its 2.88-billion-mile journey to snatch pieces of a speeding comet and bring them back to Earth.
"This is really a great day for NASA and the exploration of our solar system," said Andrew Dantzler, head of NASA's solar system division.
Tom Duxbury, project manager at JPL, said: "This thing went like clockwork."
Launched Feb. 7, 1999, Stardust made two loops around the sun before meeting up with comet Wild 2 between Mars and Jupiter in January 2004. The craft flew as close as 147 miles to the hamburger-shaped comet, passing through its tail of dust and exotic gases.
The spacecraft deployed a tennis racket-shaped collector, packed with a material called aerogel, to capture comet particles, which are thought to be the building blocks of the solar system.
Scientists won't know for a few days how many comet particles were collected, but they said early evidence pointed to a successful mission.
As Stardust neared Earth, it released a capsule containing the captured samples just before 10 p.m. Saturday. The capsule, protected by a thick heat shield, entered the atmosphere about 2 a.m., while the main spacecraft remained in orbit. High winds in the mountains of Utah pushed the capsule slightly off course during its descent.
NASA program managers still called it a "bull's-eye" landing on a surface muddied by recent rain.
Controllers were especially pleased to see the parachute open after 2004's near-disastrous end to NASA's Genesis mission. Like Stardust, Genesis was a difficult sample-return mission, the first U.S. attempt since Apollo 17 brought back moon rocks in 1972.
Genesis was returning with microscopic evidence of solar wind, the energy particles that flow out from the sun, when its parachute failed to open and the capsule "pancaked" in the Utah desert. Scientists have spent months trying to reassemble its delicate collector array. Like Genesis, Stardust was built by Lockheed Martin.
In contrast, everything seemed to go near perfectly for Stardust.
The only apparent damage was the loss of small bits of the heat shield due to the tremendous temperatures the capsule experienced on its return trip. Because of the complicated geometry of the journey, Stardust reentered the Earth's atmosphere at a higher speed than any spacecraft in history -- 29,000 mph.
On Sunday, technicians at Dugway removed the science materials, including the aerogel collector in which the particles bury themselves like a baseball going into a mitt, for shipment to the Johnson Space Center in Houston.
Mission scientists hope they captured thousands of particles. The largest they expect to find are about one-fifth of an inch in diameter. Most are likely to be in the range of microns, thinner than a human hair.
"The real touchdown will be when we open it up Tuesday ... and figure out how many particles we did capture," said Joe Vellinga, Lockheed Martin's Stardust manager.
The dust and ice particles captured by Stardust will help scientists understand the complex chemical and physical processes that lead to the formation of planets around stars.
Comets are some of the oldest and least tainted objects in the solar system.
"The most interesting thing about comets is they are libraries with the stored records of our formation," said Donald Brownlee of the University of Washington, the mission's principal investigator.
"All the atoms on Earth and in our bodies were in stardust before the solar system formed."
Originally thought to be dirty ice balls, evidence collected from last summer's Deep Impact mission -- which sent a probe into comet Tempel 1 -- showed they would be more accurately characterized as icy dirt balls, composed of what Brownlee called an "organic goo."
The dirt of a comet is not like dirt on Earth. However, scientists theorize that comets could have seeded an early Earth with some of the molecular building blocks of life. Lending weight to this idea was the 1979 discovery of a meteorite in Australia containing amino acids.
Looking at the components of a comet such as Wild 2 is like looking back in time billions of years.
Unlike the loosely-arranged, oblong-shaped Tempel 1, Wild 2 is rounder, with rugged features that include craters and cliffs 300 feet tall. "It's very bizarre," Brownlee said.
Both comets are about a mile across.
Wild 2 (named after its Swiss discoverer and pronounced Vilt) belongs to the Jupiter family of comets, spending most of its time orbiting between the giant gas planet and Mars. It hasn't always been there. It originally orbited near Uranus and is thought to have formed 4.5 billion years ago in the Kuiper Belt, the region of icy planetoids beyond Neptune.
A close encounter with Jupiter in 1974 knocked it out of its original orbit and sent the comet spinning into the inner reaches of the solar system, where the sun's rays are causing it to spout dust and ice and gas like a fountain.
"It's coming apart under the heating of the sun," Brownlee said.
This spewing behavior made Wild 2 a perfect candidate for the $200-million Stardust mission.
But all this off-gassing is costing the comet its very existence. In less than 10,000 years, Brownlee said, Wild 2 will be no more.
The super-lightweight aerogel material used to catch the comet particles has been used on several previous missions to capture interstellar materials.
When the particles are retrieved from the gel, they will be shipped to about 150 scientists around the world for analysis.
Scientists will be studying the material captured by Stardust for decades. Meanwhile, the spacecraft that carried the capsule and its scientific instruments remains out in space, awaiting further orders.
NASA said Sunday that Stardust might entertain other missions, though the craft wouldn't be able to bring anything else back home.
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A capsule from the Stardust spacecraft returned to Earth on Sunday after completing a seven-year journey to collect comet and interstellar dust particles. It was launched Feb. 7, 1999.
1. Jan. 15, 2001: Swung around Earth for a gravity boost.
2. March-May and July-December 2002: Collected interstellar dust.
3. Jan. 2, 2004: Encountered comet Wild 2 and collected comet dust.
4. Sunday: Returned to Earth.
Aerogel in space
Stardust collected particles with the help of a material called aerogel.
Speeding particles embed themselves in the lightweight aerogel.
Dust is collected on a honeycomb-like tray containing solid aerogel blocks.
Sample particles are placed in a protective capsule.