Stardust Capsule Lands With Comet Dust Sample
SAN JOSE, Calif. _ After an epic journey of 2.9 billion miles, the Stardust capsule landed in the Utah desert Sunday morning with a thimbleful of comet dust _ the first samples from a comet ever brought back to Earth.
Researchers on a NASA DC-8 research plane whooped with delight as the capsule appeared at 1:57 a.m., midway between Mars and the constellation Pleiades. It flared into a brilliant white fireball that turned reddish-gold and sprouted a long, thin tail of glowing vapor.
“Isn’t it gorgeous?” said Peter Jenniskens, a meteor expert with the SETI Institute in Mountain View, Calif., and lead scientist for the airborne mission. “It’s a meteor _ a manmade meteor.”
The capsule streaked into the atmosphere at nearly 29,000 mph, faster than any human-made object before it, and was expected to reach nearly 5,600 degrees Fahrenheit _ about 25 times as much heat as the space shuttle endures.
A high-definition television camera on board the NASA plane showed a small, glowing object that appeared to come off the capsule just before it passed out of view.
Examining the video, scientists on the flight said they could not tell whether it was a natural meteor that just happened to coincide with Stardust’s manmade fireball or a piece of the capsule’s heat shield that fell away.
If part of the heat shield did come off, the capsule could heat up more than expected, said George A. Raiche, an atmospheric chemist at NASA’s Ames Research Center in Mountain View who works on heat shield development and testing. He added that “a very small particle could give a disproportionately bright signal,” and that the only way to tell if the capsule had been significantly damaged was to look it over.
NASA officials said the capsule, which bounced five times to a muddy landing at the Utah Test and Training Range southwest of Salt Lake City, appeared to be in excellent shape, although bits of the heat shield were found nearby.
It was taken by helicopter to a temporary clean room at nearby Michael Army Air Field. There researchers removed the canister that holds the dust samples and flooded it with ultra-pure nitrogen gas to keep it pristine.
On Tuesday it will be flown to Johnson Space Center in Houston and housed in the same building as moon rocks and meteorites. Bits of dust will be distributed for preliminary analysis to 150 scientists worldwide, including labs at Stanford University, Lawrence Livermore National Laboratory and the University of California, Berkeley.
Comet dust is surprisingly common on Earth. More than 30,000 tons of it fall onto the planet each year; California alone collects a billion times more particles every day than Stardust grabbed in its collector.
But until now there were no pure samples. Scientists longed to get one because it’s the stuff that formed the sun and planets 4.6 billion years ago _ “a frozen time capsule from the beginning of the solar system,” said John P. Bradley, head of the Institute of Geophysics and Planetary Physics at Lawrence Livermore.
Comets pummeling the young Earth are thought to have delivered some of the key ingredients for life, from water to carbon-based compounds.
And interstellar dust, which is created in stars, contains virtually all of the elements heavier than helium.
“We have always stressed in this mission that we are stardust,” said Donald Brownlee of the University of Washington, one of the lead scientists for the mission. “Our planet and even our selves have a direct relationship to the particles we brought back.”
Launched seven years ago, the $168 million spacecraft spent months gathering interstellar dust, which is so sparse that only a few dozen particles are thought to have lodged in the collector.
Two years ago it came within 149 miles of Comet Wild 2 _ named after its discoverer and pronounced VILT 2 _ and grabbed particles from the hazy envelope of gas and dust that surrounds the comet’s nucleus.
The samples are thought to contain millions of specks that, if lumped together, would weigh less than a grain of salt and not quite fill a thimble.
Despite their minuscule size, they should contain enough material to distribute and study for years to come. In fact, some of the bigger bits _ those larger than about 1/10 the diameter of a human hair _ may be sliced up smaller.
At the time NASA approved the Stardust mission, many of the techniques that will be used to pluck the dust particles out of their collectors and determine their makeup did not exist, Bradley said.
“There’s been a real revolution in analytical techniques in about the last 10 years,” he said last week. They include the world’s most powerful electron microscope, built at Lawrence Livermore with NASA funding, and a set of microscopic tweezers and other tools developed at the University of California, Berkeley.
As a result, Bradley said, scientists have gone from analyzing pounds of moon rocks “to little tiny vials of dirt. It’s a real paradigm shift.”
Brownlee said seeing photos of the capsule, home at last in a muddy salt flat, “is an incredible thrill. It’s very emotional.”
It’s ironic, he said, that a mission returning comet samples to Earth should end up looking like a comet itself.
“I fully expect that textbooks in the future will have a lot of information about the formation of the solar system from these samples that landed this morning in Utah,” Brownlee said.
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