The United Launch Alliance Atlas V rocket carrying NASA's Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft lifts off from Space Launch Complex 41 at Cape Canaveral Air Force Station, Florida, US in this September 8, 2016 handout photo. [Photo/Agencies]

WASHINGTON -- 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 blasted off atop an Atlas V rocket at 7:05 p.m. EDT (2305 GMT) as planned from Cape Canaveral Air Force Station in Florida.

"Liftoff!" a NASA TV commentator said during a live broadcast. "It's a seven-year mission to boldly go to asteroid Bennu and back."

The 800-million-US.-dollar mission's main goal is to collect a small sample of rocks and surface soil from Bennu, thought to harbor 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," said SIRIS-REx principal investigator Dante Lauretta of the University of Arizona. "This is going to be a treasure trove of material for scientists yet to come."

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.