Washington, Sep 9 (AZINS) US space agency NASA on Thursday launched the nation's first mission that will visit an asteroid and bring precious samples back to Earth.

The Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft lifted off atop an Atlas V rocket at 7:05 p.m. EDT (2305 GMT) as planned from Cape Canaveral Air Force Station in Florida, Xinhua news agency reported.

The $800 million mission's main goal is to collect a small sample of rocks and surface soil from Bennu, thought to harbour primordial material left over from the formation of the solar system 4.5 billion years ago.

"Sample return is really at the forefront of planetary exploration. This is going to be a treasure trove of material for scientists yet to come," said SIRIS-REx principal investigator Dante Lauretta of the University of Arizona. 

If all goes according to plan, OSIRIS-REx will arrive in August 2018 and spend the next two years photographing and mapping the asteroid's surface to better understand its chemical and mineralogical composition, including selecting the sample site.

Then, in July 2020, the spacecraft will touch the asteroid for only three seconds to collect at least 60 grams of loose rocks and dust using a device called the Touch-and-Go Sample Acquisition Mechanism and store the material in a sample return capsule.

The spacecraft will depart the asteroid in March 2021 and travel for two-and-a-half years on a trajectory for Earth return in September 2023.

But OSIRIS-REx won't land. Instead, it will eject a small capsule containing the asteroid sample, which will land with the help of parachutes at the Utah Test and Training Range, southwest of Salt Lake City.

The main spacecraft will remain in orbit around the Sun after the sample return and Earth flyby.