A spacecraft has delivered asteroid samples to Earth after travelling through deep space for seven years.
The Osiris-Rex spacecraft flew close to Earth on Sunday and dropped a capsule carrying 250 grams of soil from the asteroid Bennu, a celestial object that could help scientists learn more about the formation of the Solar System.
It carried out a parachute-assisted landing in a remote Utah desert and was then transported in a helicopter to Texas, so it could be secured inside a clean room.
The US has now become the second country, after Japan, to bring back asteroid samples.
"Congratulations to the Osiris-Rex team on a picture-perfect mission – the first American asteroid sample return in history – which will deepen our understanding of the origin of our Solar System and its formation," said Nasa administrator Bill Nelson.
"Not to mention, Bennu is a potentially hazardous asteroid, and what we learn from the sample will help us better understand the types of asteroids that could come our way."
How did the Osiris-Rex secure samples?
Bennu is a near-Earth asteroid that was first discovered in 1999 and is said to be formed from materials that date back billions of years.
The sample collection was a complex process because there was an 18.5-minute delay in sending and receiving signals between mission control and the craft due to the distance.
Navigation cameras on the capsule helped it successfully reach the asteroid.
Bennu orbits the sun at 101,388kph. Osiris-Rex was programmed to travel towards it at about 19,400kph and slow itself down on approach.
Once close enough, the spacecraft extended its robotic arm and vacuumed up samples.
How did the craft deliver the asteroid soil back to Earth?
After travelling billions of kilometres to Bennu and back, the spacecraft released its sample capsule towards Earth’s atmosphere at 2.42pm, UAE time.
The spacecraft was 102,000km from Earth’s surface at the time – about one-third of the distance from Earth to the Moon.
The capsule entered the atmosphere at 6.42pm while travelling at 27,650km and, within 10 minutes, it landed on a military range in a Utah desert.
Two parachutes that deployed helped to stabilise and slow the capsule down.
"Curation scientists there will disassemble the canister, extract and weigh the sample, create an inventory of the rocks and dust, and, over time, distribute pieces of Bennu to scientists worldwide," Nasa said.
Scientists will be studying the samples from asteroid Bennu.
But the spacecraft that delivered them will now depart to another asteroid for its next mission.
It is making its way to asteroid Apophis, with the craft now renamed from Osiris-Rex to Osiris-Apex.
Scientists are concerned about Apophis because it is expected to come about 32,000km of Earth in 2029, which is less than one-tenth the distance between Earth and the Moon.
"Osiris-Apex is scheduled to enter orbit of Apophis soon after the asteroid’s close approach of Earth to see how the encounter affected the asteroid’s orbit, spin rate and surface," Nasa said.