The largest haul of extraterrestrial samples since Apollo 17 landed in the western Utah desert on Sept. 24, marking the end of a seven-year, 4-billion-mi. mission to the asteroid Bennu in a quest to learn more about the primordial Solar System, resources for potential future exploitation and the Yarkovsky effect, which has implications for planetary defense.

The mission began on Sept. 8, 2016, with the launch of NASA’s $1 billion Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (Osiris-REx) spacecraft aboard a United Launch Alliance Atlas V from Cape Canaveral.

Two years later, the solar-powered Osiris-REx—built by Lockheed Martin—arrived at Bennu, a carbon-rich near-Earth asteroid discovered in 1999 and later classified as a potential hazard object. The spacecraft circled the pebble-strewn, 1,650-ft.-dia. Bennu scouting for a suitable site to fulfill its mission: collecting at least 60 grams of rocks and soil and returning them Earth.

On Oct. 20, 2020, as scientists and flight controllers monitored from 200 million mi. away, Osiris-REx descended to the surface and used an 11-ft.-long robotic arm to collect small rocks and dust from a small crater named Nightingale.

The touch-and-go maneuver ended up with an estimated 250 grams of material—more than four times the mission objective. On May 10, 2021, Osiris-REx departed Bennu to begin the trip back to Earth.

Following a 12th and final trajectory-correction maneuver on Sept. 17, Osiris-REx deployed its blunt-nosed 3-ft.-dia.,100-lb. Sample Return Capsule (SRC) holding the precious cargo at 6:42 a.m. EDT on Sept. 24 as the mothership flew about 63,000 mi. from Earth.

Four hours later and now traveling at a speed of 27,650 mph, the SRC hit the top of Earth's atmosphere about 82 mi. off the coast of San Francisco. The spacecraft, tracked by infrared cameras aboard a NASA WB-57 high-altitude aircraft, blazed eastward as it headed toward a 36-by-8.5-mi. landing zone at the U.S. military’s Utah Test and Training Range, located about 80 mi. west of Salt Lake City.

At 10:52 a.m.—3 min. earlier than planned due to a premature parachute deployment—the charred capsule landed on the desert floor. Recovery teams located the capsule, checked it for any unexploded ordnance and toxic gas emissions, and then transported it via helicopter to a temporary cleanroom set up at the range.

The SRC was to be disassembled so the canister holding the Bennu samples can be flown to NASA’s Astromaterials Curation Facility at Johnson Space Center in Houston on Sept. 25.

The mission marks NASA’s first to obtain samples from an asteroid and followed missions to collect rocks, soil and dust from the Moon, a comet and the solar wind.  Japan has twice returned samples from two asteroids.

Meanwhile the Osiris-REx mothership—which made its closest approach to Earth when the SRC reached peak heating of 5,000F and a maximum deceleration force that was 32 times the force of gravity—was recommissioned for a follow-on mission to another near-Earth asteroid:  the 1,000-ft.-dia. Apophis, which will come within 20,000 mi. of Earth in 2029.

The newly renamed Osiris-APEX spacecraft is scheduled to put itself into orbit around Apophis soon after the asteroid’s close approach to study how the encounter with Earth affected the asteroid’s orbit, spin rate and surface.