OSIRIS-REx Bennu Sample Collection

On October 20, 2020, NASA’s OSIRIS-REx spacecraft executed a daring “Touch-And-Go” maneuver, briefly contacting asteroid Bennu’s surface to collect samples—discovering the surface far less solid than expected, with the sampling arm sinking deep into “fluffy” material before nitrogen gas blasted 60+ grams of regolith into the collection chamber.

The sampling event exceeded expectations dramatically: the spacecraft’s TAGSAM (Touch-And-Go Sample Acquisition Mechanism) collected so much material that rocks jammed the container’s mylar flap, allowing precious particles to escape into space. Mission control rushed to stow the sample head into the return capsule days ahead of schedule to prevent further loss.

Videos of the sampling showed the spacecraft’s arm plunging into Bennu’s surface like “a pit of plastic balls,” upending assumptions about asteroid structure. Scientists realized rubble-pile asteroids like Bennu are loosely held together by gravity rather than structural integrity—critical information for planetary defense (kinetic impactors might not work) and resource extraction.

The mission studied Bennu from December 2018-May 2021, mapping every square meter to find safe sampling sites on a surface more rugged and boulder-strewn than anticipated. Bennu’s rapid rotation, active particle ejections, and unexpectedly rough terrain forced multiple landing site changes, demonstrating asteroid missions’ unpredictability.

OSIRIS-REx departed Bennu in May 2021, returning samples to Utah desert on September 24, 2023—NASA’s first asteroid sample return. Early analysis revealed 4.5-billion-year-old carbon-rich material with water-bearing clay minerals and organic compounds, supporting theories about asteroids delivering building blocks for life to early Earth. The spacecraft continued to study asteroid Apophis under new mission name OSIRIS-APEX.

https://www.asteroidmission.org https://www.nasa.gov/osiris-rex https://www.nature.com/bennu-research