By Helen Briggs
BBC News science reporter
After a brief search, the recovery team found the capsule
Watch the landing
The Stardust probe released the capsule as it flew back to Earth after a 4.6-billion-km (2.8-billion-mile) trip.
The US-built capsule plunged through the atmosphere and touched down in the Utah desert at 0312 (1012 GMT).
Scientists believe the first cometary dust samples ever returned to Earth will shed light on the origins of the Solar System.
It is amazing to think that such minute specks of dust can carry within them so much information about the origin of stars and planets
Prof Monica Grady, PSSRI
"I fully expect textbooks in the future will have a lot of new information from the samples that landed here this morning."
Fiery descent
The Stardust spacecraft released the 45kg (100lb) capsule at 0557 GMT as it looped past the Earth on its return from interplanetary space.
A day of celebration for everyone on the Stardust project
Four hours after leaving the probe, the capsule entered the Earth's atmosphere 125km (410,000ft) over the Pacific Ocean.
It reached speeds of 46,660km/h (29,000mph) - the fastest re-entry of any manmade probe - and was visible from parts of the American northwest as a streak of light in the sky.
At about 32km altitude (105,000ft), the capsule released a small parachute to slow its descent.
The main parachute opened at about 3km (10,000ft), and brought the capsule down to land on a military base southwest of Salt Lake City.
"All stations, we have touchdown," an announcer declared to a jubilant control room.
First analysis
The capsule was located by helicopter almost an hour after the landing. It was then flown to a nearby laboratory for checks.
The capsule was prepared for onward transport to Johnson
"I'm very confident we will have samples in there that are the first returned from beyond the Moon," former Stardust project manager, Ken Atkins, told the BBC News website.
"It is magnificent to see something that we saw leave the planet on 7 February 1999 return to the planet here on 15 January 2006."
The highlight of Stardust's seven-year mission was its close encounter with Comet Wild 2 in January 2004.
The sample-return capsule was seen to streak across the sky
As part of its trip, the probe also captured a sprinkling of dust that originated in distant stars.
The Stardust mothership has now completed its main mission and has been sent into orbit around the Sun.
'Minute specks'
Meanwhile the work of scientists is just beginning. On Tuesday, Nasa experts will open the canister containing the samples which is packed away inside a protective shell.
Stardust could provide a new window into the distant past
Dr Simon Green
They are trapped inside cells filled with an ultra-light solid called aerogel.
About 150 scientists around the world will get a chance to carry out a preliminary analysis of the contents, including researchers at the UK's Open University (OU).
Stardust took remarkable pictures of Comet Wild 2
"Imagine trying to pick up a grain that is less than a hundredth of the size of the full stop at the end of this sentence," she said.
"It is amazing to think that such minute specks of dust can carry within them so much information about the origin of stars and planets."
Time capsules
Comets are thought to be cosmic "time capsules", containing material unchanged since the formation of the Sun and planets.
Some even think they may have seeded Earth with the chemical building blocks required for life.
Stardust's mission: How Nasa's probe collected comet dust and will return it to Earth
In pictures
"Because these particles have come from inside a comet, we know that essentially the particles haven't been heated since they became part of the comet, because the comet is made of ice," he told the BBC News website.
"That means that they contain information about the conditions that were present when they were incorporated into the comet.
"That time was four-and-a-half thousand-million years ago, back when the Solar System formed; so what we hope to know from these particles is essentially what the Solar System looked like at that time, and essentially what we're all made of."
An infrared camera captures a recovery helicopter at the landing site of the Stardust sample return capsule.
An infrared camera captures the Stardust sample return capsule 
as it descends to the Utah Test and Training Range.
Capsule after landing

"All stations, we have touchdown," an announcer declared.

Stardust, a capsule carrying dust from Comet Wild 2, has landed safely in the Utah desert. It also is the first time in history that a space mission has brought back such material.

"The tiny particles that the Stardust mission is bringing back are the most scientifically exciting and technically challenging material that we have ever had the opportunity to study," said Monica Grady of the Planetary and Space Science Research Institute (PSSRI).

When the landing was complete, it drew cheers from excited scientists. 

"It's an absolutely fantastic end to the mission," said Carlton Allen of NASA's Johnson Space Center.

"Everything worked so well. What an exciting moment," said Allan Cheuvront, Stardust spacecraft engineer at Lockheed Martin Space Systems. 

Many reports are stating from skywatchers, that sighted the speeding capsule as it shot across the sky over the western United States. "We saw it in the sky…it was great," said Paula Nicholson, Public Affairs Officer at the U.S. Army Dugway Proving Ground.

In 2004, another collector capsule from another spacecraft, Genesis, which collected solar wind particles crashed into the Utah desert, however, the samples did not survive.

After the capsule landed, it activated its locator beacon and helicopter recovery crews successfully located the capsule in the dark. The capsule is reportedly intact from the helicopter observations, and the unofficial touch down time was 5:10 a.m. EST. It will be transferred to a "cleanroom" and is expected to be flown to Johnson Space Center early next week where the capsule will be unlocked for the first time since it landed.

When opened, scientists will find the microscopic dust particles trapped in a porous, pale-blue smokelike material known as aerogel made up of 99.8 percent air that was used to snag the dust in space. 

The dust then will be looked at under a microscope to be examined and because this comet is nearly 5 billion years old, they hope it will unlock some of the secrets to the formation of our galaxy and universe.

The capsules speed when it was going through Earth's atmosphere was a record breaking 29,000 mph, making it the fastest man-made probe to return to Earth. Its first parachute opened at nearly 100,000 feet from the ground where it was then guided to a 10-MPH landing in the desert.

The capsule also brought back with it 72 black-and-white pictures showing broad mesas, craters, pinnacles and canyons with flat floors on the surface of Wild 2, which was a staggering 500 million miles from Earth at the time Stardust was launched.

Stardust was launched in 1999 and its trip lasted over 7 years. Stardust traveled about 4.5 billion kilometers (2.88 billion miles), and went around the sun 3 times. In the end, a magnificent achievement for NASA and science in general.