A space capsule ferrying the first comet dust samples to Earth parachuted to a pre-dawn landing in the remote desert yesterday, drawing cheers from elated scientists.
The touchdown capped a seven-year journey by NASA's Stardust spacecraft, which zipped past a comet in 2004 to capture minute dust particles and store them in the capsule for the homecoming.
"It's an absolutely fantastic end to the mission," said Carlton Allen of NASA's Johnson Space Center.
A helicopter recovery team was searching the landing site for the capsule and was expected to transfer it to a clean room on the base. It will be flown later this week to the Johnson Space Center in Houston where scientists will unlock the canister containing the cosmic particles.
Once opened, they will find the microscopic bits trapped in a porous, pale-blue smokelike material made up of 99.8 percent air that was used to snag the dust in space.
The dust will be viewed under a microscope and analyzed. Because comets are frozen bodies of ice and dust from 4.6 billion years ago when the solar system was formed, researchers hope the comet dust will provide direct clues about the origin of our planetary system.
The cosmic samples were gathered from comet Wild 2 in 2004 during Stardust's seven years in space. The spacecraft used a tennis racket-sized collector mitt to snatch the dust and store it in an aluminum canister.
The capsule nose-dived through the Earth's atmosphere early yesterday at a record 29,000mph (47,000kph), making it the fastest unmanned probe to return.
As it descended toward the desert, it unfurled its first parachute at 100,000 feet (30,000m) followed by a larger chute, which guided it to a gentle landing on the salt flats.
The mission, managed by NASA's Jet Propulsion Laboratory, cost US$212 million.
Stardust's return to Earth was the reverse of the ill-fated Genesis mission that carried solar wind particles.
In 2004, Genesis slammed into the desert and broke open like a clamshell, exposing the solar atoms to contamination.
Researchers believe about 1 million samples of comet and interstellar dust -- most tinier than the width of a human hair -- are locked inside the capsule.
The cosmic dust should keep researchers busy for years. They hope to slice the samples into smaller bits and probe them under a microscope to directly learn about their chemical makeup and the processes that shaped the early universe.
The dust grains, believed to be pristine leftovers from the birth of the solar system, contain many of the organic molecules necessary for life.
Some of the captured particles are thought to be older than the sun.
Stardust's comet samples represent the second robotic retrieval of extraterrestrial material since 1976, when the unmanned Soviet Luna 24 mission brought back lunar rocks and soil.
Launched in 1999, the Stardust spacecraft traveled nearly 4.8 billion kilometers, looping around the sun three times.