In just a few hours, the world will know whether NASA’s OSIRIS-REx spacecraft successfully reached out and touched Bennu, a tiny, top-shaped asteroid that’s been spinning through the solar system for a billion years. During the maneuver, the spacecraft will swoop down, scoop up a bit of material, and depart seconds later with precious cargo: rocks and dust dating back to the solar system’s birth.
The mission is humankind’s third attempt—and NASA’s first—to sample the surface of an asteroid. The first two asteroid sampling missions, performed by Japan’s Hayabusa and Hayabusa2 spacecraft, picked up only small amounts of fine-grained material. By contrast, OSIRIS-REx is designed to pick up as much as 4.4 pounds of material that ranges in size from tiny grains to two-centimeter-wide pebbles.
Assuming all goes well, a radio dish in Spain will receive the signal that OSIRIS-REx completed its task at 6:12 p.m. ET on October 20. The spacecraft will depart Bennu in March 2021, reaching Earth two and a half years later to eject the sample-filled capsule, which will parachute to the deserts of Utah for collection and study.
If successful, OSIRIS-REx will provide a wealth of insight into Bennu’s history, and perhaps help scientists better understand the origins of water and life on Earth.
“Asteroids are like time capsules floating in space that can provide a fossil record for the birth of our solar system,” Lori Glaze, the director of NASA’s planetary science division, said in a press briefing on October 19. “They can provide valuable information about how the planets—including our own—came to be.”
Some space rocks also pose a threat to life’s future—and that includes Bennu. NASA estimates there’s a 1-in-2,700 chance of Bennu colliding with Earth sometime in the late 2100s. Decades from now, if future measurements confirm a collision course, data from OSIRIS-REx would help scientists monitor the asteroid and alter its orbit to avert a potentially catastrophic impact.
Flying to an ancient world
Getting to Bennu has been a hard, 16-year journey for the mission team.
Though the mission was first conceived in 2004, NASA didn’t formally select it to fly until May 2011. Mere months later, OSIRIS-REx’s original leader, University of Arizona planetary scientist Mike Drake, died after a prolonged illness following liver failure. Drake’s deputy, Dante Lauretta, stepped into the role left by his mentor, and the mission has been carried out in Drake’s memory. After launching on September 8, 2016, OSIRIS-REx traveled tens of millions of miles to arrive at Bennu in December 2018.
The spacecraft is one of the most complex missions NASA has ever operated around another world.
Bennu is the smallest celestial body a spacecraft has ever orbited: a mere rubble pile less than 1,700 feet wide on average, barely held together by its