NASA has formally concluded the OSIRIS-REx mission, marking the end of the historic U.S. effort to collect and return a pristine piece of an asteroid to Earth. The van-sized spacecraft, whose name stands for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, spent years traveling to the ancient space rock Bennu to retrieve remnants dating back more than 4.5 billion years to the dawn of the solar system.
The formal closure of the mission took place on Sept. 30, following nearly a decade of high-stakes engineering, troubleshooting, and scientific discovery. The $1 billion project, funded under NASA’s New Frontiers Program, required approval in 2011 after facing two initial rejections.
When OSIRIS-REx launched on Sept. 8, 2016, scientists anticipated finding a smooth, sandy surface on Bennu. Instead, upon arrival in late 2018, the probe revealed a treacherous, loosely bound amalgamation of jagged boulders. Principal Investigator Dante Lauretta noted that expectations about the asteroid’s surface were entirely incorrect, leaving no obvious touchdown spot.
The spacecraft ultimately touched down on a small crater named Nightingale. The surface offered so little structural resistance that it reacted more like a fluid than a hard rocky shell, allowing the sampling head to sink 20 inches deep before firing thrusters to pull away with the sample.
Complications arose when the sample collector lid became jammed in a partially open position due to the sheer volume of material retrieved, allowing some fragments to escape. The team quickly stowed the sampler head inside the return capsule to prevent further loss. The mission’s return to Earth on Sept. 24, 2023, featured another tense moment when a parachute failed to deploy properly, though the capsule still achieved a safe landing in the Utah desert.
Prior to sample collection, the probe set a Guinness World Record by entering orbit around the 1,610-foot-wide Bennu, making it the smallest object ever circled by a spacecraft. Remote-sensing observations subsequently confirmed that Bennu is coated in carbon-bearing compounds and was once part of a much larger, water-rich parent asteroid that shattered in the main asteroid belt between Mars and Jupiter.
The returned material weighs 4.29 ounces on Earth, more than double the mission’s initial requirement. Researchers have already published more than 200 papers examining the sample, uncovering amino acids, sugars, and evidence of liquid water exposure that could mirror the early conditions that seeded life on Earth. Most of the sample is being preserved for future generations using advanced technology not yet available.
Though the OSIRIS-REx chapter is finished, the spacecraft itself remains active. Renamed OSIRIS-APEX, for OSIRIS-APophis EXplorer, the probe is currently using its remaining propellant to travel toward Apophis, a different type of near-Earth asteroid, with arrival scheduled for 2029.
