New York (dpa) - A NASA spacecraft carrying a large sample collection from the asteroid Bennu on Monday set off on its return trip to Earth after nearly five years in space.

The spacecraft Osiris-Rex - short for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer - fired its main engines full throttle at 2023 GMT, setting off for a 2.5-year return trip to Earth, the US space agency said.

In October, Osiris-Rex conducted NASA's first sample collection from an asteroid as part of its seven-year long voyage. Bennu is a black pile of rubble about 500 metres wide and located some 290 million kilometres from Earth.

After orbiting the Sun twice, the spacecraft is due to reach Earth on September 24, 2023.

"OSIRIS-REx's many accomplishments demonstrated the daring and innovate way in which exploration unfolds in real time," said Thomas Zurbuchen, associate administrator for science at NASA Headquarters.

"The team rose to the challenge, and now we have a primordial piece of our solar system headed back to Earth where many generations of researchers can unlock its secrets."

NASA hopes the 1-billion-dollar mission will reveal secrets about the origins of our solar system. Asteroids are remnants from that era, more than 4.5 billion years ago.

Osiris-Rex was launched from the space port Cape Canaveral in Florida in September 2016. It took about two years to arrive within 20 kilometres of Bennu and a further two to find an ideal spot for collecting the sample.