In a flyby of Earth, the Osiris-Rex spacecraft released the sample capsule from 100,000 kilometres out.

The small capsule, containing samples from the asteroid Bennu, landed four hours later on a remote expanse of military land, as the mothership set off after another asteroid.

"We have touchdown!" Flight Control announced, immediately repeating the news, since the landing occurred three minutes before anticipated. 

Officials later said the orange-striped parachute opened four times higher than anticipated — around 6,100 metres — which led to the early touchdown.

To everyone's relief, the capsule was intact and had not been breached, keeping its 4.5-billion-year-old samples free of contamination.

Within two hours of touchdown, the capsule was inside a temporary clean room at the US Defense Department's Utah Test and Training Range, having been hoisted there by helicopter.

The sealed sample canister will be flown on Monday to NASA's Johnson Space Center in Houston, where it will be opened in a new, specially designed lab.

The building already houses the hundreds of kilograms of moon rocks gathered by the Apollo astronauts.

At a news conference several hours later, the mission's lead scientist, Dante Lauretta of the University of Arizona, said he broke into tears of joy upon hearing that the capsule's main parachute had opened.

He said he was so overwhelmed with emotion when he arrived at the scene that he wanted to hug the capsule.

"Boy, did we stick that landing," Dr Lauretta said. "It didn't move, it didn't roll, it didn't bounce. It just made a tiny little divot in the Utah soil."

"We can't wait to crack into it. For me, the real science is just beginning."

Another Osiris-Rex team member was stuck in England, rehearsing for a concert tour.

"My heart's there with you as this precious sample is recovered," said Queen lead guitarist Brian May, who is also an astrophysicist.

"Happy Sample Return Day."

A view back in time, and future protection

NASA Administrator Bill Nelson said the samples will provide “an extraordinary glimpse into the beginnings of our solar system".

With these samples, "we are edging closer to understanding its early chemical composition, the formation of water, and the molecules life is based on," astronomer Daniel Brown of Nottingham Trent University in England said.

Currently orbiting the sun 81 million kilometres from Earth, Bennu is about one-half of a kilometre across, roughly the size of the Empire State Building but shaped like a spinning top.

It is believed to be the broken fragment of a much larger asteroid.

The space rock is classified as a "near-Earth object" because it passes relatively close to our planet every six years.

Bennu is expected to come dangerously close to Earth in 2182 — possibly close enough to hit.

The data gleaned by Osiris-Rex will help with any asteroid-deflection effort, according to Dr Lauretta.

Osiris-Rex, the mothership, rocketed away on the $US1 billion ($1.55 billion) mission in 2016.

It reached Bennu two years later and, using a long stick vacuum, grabbed rubble from the small roundish space rock in 2020.

By the time it returned, the spacecraft had logged 6.2 billion kilometres.

'Real moment of truth' to come:

NASA's recovery effort in Utah on Sunday included helicopters as well as a temporary clean room set up at the Defence Department's Utah Test and Training Range.

The pebbles and dust contained in the capsule likely represent the biggest haul of matter ever brought home from beyond the moon.

Scientists estimate the capsule holds at least a cup of rubble from the carbon-rich asteroid, or about 250 grams, but will not know for sure until the container is opened in Houston, a moment Dr Lauretta called "the real moment of truth".

Some of the samples spilled and floated away when the spacecraft scooped up too much and rocks, jamming the container's lid during collection three years ago.

Even at the low end of the estimates, however, the amount will easily surpass the minimum requirement of the mission, Dr Lauretta said.

It will take a few weeks to get a precise measurement, said NASA's lead curator Nicole Lunning.

Japan, the only other country to bring back samples, gathered about a teaspoon during a pair of asteroid missions.

NASA is planning to hold a public show-and-tell of the recovered samples in October.

Source | AP