A NASA spacecraft briefly touched an asteroid on Wednesday to collect dust and rock samples that it will slowly bring back home.

The asteroid, Bennu, is around 321 million kilometres away from Earth and has had the OSIRIS-REx spacecraft in its orbit since late 2018.

Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate, called the asteroid tag “an incredible feat”.

“Today we’ve advanced both science and engineering and our prospects for future missions to study these mysterious ancient storytellers of the solar system,” Zurbuchen said.

“A piece of primordial rock that has witnessed our solar system’s entire history may now be ready to come home for generations of scientific discovery, and we can’t wait to see what comes next.”

With a suitable, boulder-free location scouted out and OSIRIS-REx in place, it began an autonomous maneuver, pre-programmed by engineers on Earth, to de-orbit and reach out its three-metre long arm in anticipation.

It took about four hours for OSIRIS-REx to travel the 800 metres from orbit to surface where it touched the surface and fired a short burst of nitrogen gas to stir up debris that it collected for the long journey home.

NASA’s scientists will spend about a week making sure the sample of dust and regolith is sufficient before deciding whether to send OSIRIS-REx home or make another attempt at touching down and gathering material.

“After over a decade of planning, the team is overjoyed at the success of today’s sampling attempt,” said Dante Lauretta OSIRIS-REx principal investigator at the University of Arizona.

“Even though we have some work ahead of us to determine the outcome of the event – the successful contact, the [nitrogen] gas firing, and back-away from Bennu are major accomplishments for the team.

“I look forward to analysing the data to determine the mass of sample collected.”

Bennu was chosen for this mission from over 500,000 asteroids in the Solar System.

NASA picked it because of its relative proximity to Earth, large diameter (around 500 metres) and ‘primitive’ carbon-rich composition that would not have “significantly changed” since its formation some four billion years ago and could thus help unlock more information about the source of life on Earth.

No one will get to examine Bennu’s ancient space dust for a while as OSIRIS-REx will take nearly three years to return home.

OSIRIS-REx was not the first spacecraft to gather dust from a near-Earth object like Bennu.

The Japan Aerospace Exploration Agency has launched two missions – Hayabusa and Hayabusa2 – which have both gathered small amounts of material from their asteroid targets.

Hayabusa2 and its asteroid samples are due to land in Woomera, South Australia, in December.