2nd LD writethru: U.S. launches nation's first mission to collect asteroid samples

U.S. 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-U.S.-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.

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

Scientists have previously studied pieces of asteroids for decades in the form of meteorites, but all of them were quickly contaminated when they fell to Earth, Lauretta said, noting that the sample returned from a primitive asteroid would enable precise analyses that can't be duplicated on the ground.

"We expect these samples will contain organic molecules from the early solar system that may give us information and clues to the origin of life," he said.

The seven-year journey will also help explore how Bennu's orbit is affected by the so-called Yarkovsky effect, the slight push created when the asteroid absorbs sunlight and re-emits that heat as infrared radiation, in the hope of better understanding the hazards of near-Earth space rocks to Earth.

Bennu, with a diameter of 492 meters, is classified as a potentially hazardous object, with a 1 in 2700 chance of impacting Earth in the 22nd century. Lauretta said its orbit has changed by over 160 kilometers due to the Yarkovsky effect since it was discovered in 1999.

"We really want to understand this phenomenon, so that we can better understand asteroid Bennu and apply that understanding to all asteroids not only in near-earth space but throughout our solar system," he said.

The world's first asteroid sample-return spacecraft was Japan's Hayabusa 1, which successfully brought back thousands of dust grains from the asteroid 25143 Itokawa after a seven-year space trip.

Its successor, Hayabusa-2, which blasted off in 2014, is now on its way to rendezvous with the asteroid 1993 JU3 in June 2018. Enditem