October 5, 2023
Just after dawn on 24 September 2023, a fireball streaked over the American West. Inside it, sealed in a capsule the size of a truck tyre, rode a cupful of asteroid Bennu. Released four hours earlier by its mothership some 102,000 kilometres out, the capsule hit the atmosphere at 44,500 kilometres per hour, endured re-entry heating near 5,000 degrees Fahrenheit, and thirteen minutes later swung gently beneath its parachute onto the mud flats of the Utah Test and Training Range. Recovery helicopters converged on a charred container holding pristine rubble from the dawn of the Solar System.
The journey had taken seven years and roughly 6.2 billion kilometres. Launched on 8 September 2016, OSIRIS-REx reached the carbon-rich asteroid Bennu in 2018 and spent two years mapping a body that confounded expectations, a rubble pile so loosely bound that when the sampling arm touched down in October 2020, the surface parted like a ball pit. The probe sank half a metre into the asteroid and would have kept going had its thrusters not fired. It grabbed so much material that the sampler's flap wedged open, bleeding precious grains into space until engineers stowed the sample early.
The capsule's contents exceeded every requirement: 121.6 grams of Bennu, double the mission's goal and the largest asteroid sample ever returned to Earth. Even the curation became a saga; two stubborn fasteners kept part of the sample sealed until January 2024, when technicians freed them with custom-built tools. Inside waited water-bearing clay minerals, abundant carbon and, as analyses deepened, amino acids, all five nucleobases used by life on Earth, and salts left behind by ancient evaporating brines. The spacecraft itself never came home; renamed OSIRIS-APEX, it flew onward toward asteroid Apophis and its hair-raising 2029 brush with Earth.
“Congratulations to the OSIRIS-REx team on a picture-perfect mission – the first American asteroid sample return in history.”
Launch
8 Sep 2016 (Atlas V, Cape Canaveral)
Sample collected
20 Oct 2020 (Nightingale site, Bennu)
Capsule landing
24 Sep 2023, 08:52 MDT (Utah Test and Training Range)
Sample mass
121.6 g
Total journey
~6.2 billion km
Re-entry speed
44,500 km/h
Bennu's surface behaved like a ball pit; the spacecraft sank half a metre during its brief touch-and-go and had to thrust its way back out.
It collected so much rubble that the sampler head jammed open and leaked grains into space, forcing NASA to stow the sample ahead of schedule.
At 121.6 grams, the returned sample doubled the mission requirement and is the largest ever collected from an asteroid.
Two stuck fasteners kept part of the sample sealed for months; curators finally opened the canister in January 2024 using tools custom-built for the job.
The mothership never landed; renamed OSIRIS-APEX, it is flying on to asteroid Apophis, which in 2029 will pass closer to Earth than geostationary satellites.
OSIRIS-REx delivered the United States' first asteroid sample and the largest haul of extraterrestrial material brought home since Apollo. Sample return is the gold standard of planetary science, and Bennu's grains, rich in organics, hydrated minerals and brine residues, now anchor laboratory studies of how water and prebiotic chemistry reached the early Earth. The mission also proved out proximity operations at a hazardous rubble-pile asteroid, experience that feeds directly into planetary defence planning for objects like Apophis, which its renamed successor OSIRIS-APEX is en route to study.