Is capsule's comet dust key to life's origins?

• NASA probe returns to Earth after capturing 4.5bn-year-old particles

• Record-breaking probe brings back samples from farthest ever distance

• Particles to be stored in Milton Keynes and displayed in exhibition around UK

Key quote

"It is the first time particles have been brought back. They fall on Earth all the time and we think some of them come from comets, but we don't know that. We'll now be able to examine and compare them" - Professor Monica Grady, of the Planetary and Space Science Research Institute

Story in full A SPACE capsule ferrying the first comet dust samples to Earth parachuted on to a remote stretch of the Utah desert yesterday, marking a milestone in the quest to reveal how life began.

The US probe Stardust released the capsule as it flew over Earth after a seven-year, three-billion-mile NASA mission.

It is the first time that a space mission has brought back such material.

Now back on Earth, it will be a British team of scientists who will head the research into what the tiny particles can reveal.

It is believed the particles date back 4.5 billion years to the birth of the solar system, and could also contain the building blocks which formed the Earth.

Professor Monica Grady, of the Planetary and Space Science Research Institute (PSSRI), which will carry out the work, said it was one of the most significant projects the institute had ever worked on.

She said: "It is the first time particles have been brought back. They fall on Earth all the time and we think some of them come from comets, but we don't know that. We'll now be able to examine and compare them.

"It is also the first time particles have been brought back from so far away, and from so far back in time. It's really exciting.

"To understand the solar system we think dust particles made the planets, but this dust got left over as it was so far away, and got mixed up with the ice that was the comet. That's why we have been able to catch it.

"It is possible that they could be the building blocks of where life came from."

The material will be stored in a special clean room at the PSSRI base at the Open University's headquarters in Milton Keynes, to avoid any contamination or deterioration.

Initial tests will record the size, shape and colour of the dust, and what it is made from. After the preliminary work, some of the particles will be split apart for more detailed tests.

Each particle measures just a thousandth of a millimetre, so scientists will have to use electronic microscopes to see them.

Some of the particles will be put on display in a national exhibition that will visit Glasgow in September.

"We are hoping to know for the first time what these particles are made from," Prof Grady said.

"They've had no outside conditions like the other material we have worked with.

"It could be that star and comet dust are made from the same material. That is what is exciting - we don't know.

"The work will take us years and years to find out as much as we can. The technology and equipment we use improves all the time, so we have to wait for that to do more tests."

The PSSRI was first approached by NASA two years ago to help with the project.

Stardust set off in February 1999 to orbit permanently around the sun. An onboard capsule, similar to a tennis racket, was released in January 2004 to catch dust from a comet, CometWild2, as it flew within 149 miles.

The capsule, which weighed 101lb, was released yesterday morning as it flew over Earth.

Four hours after leaving the probe, the capsule entered the Earth's atmosphere, recording the fastest ever re-entry speed for a man-made probe - 29,000mph.

Two parachutes were released to slow down its descent, and it landed at a military base south-west of Salt Lake City, Utah.