A visitor from the early solar system
On September 24, 2023, a 46-kilogram capsule streaked through Earth's atmosphere at over 44,500 kilometers per hour. It landed under parachute in the Utah Test and Training Range, a restricted area of desert managed by the U.S. Department of Defense. Inside was the first-ever asteroid sample collected by a U.S. mission: 121.6 grams of rock and dust from the asteroid 101955 Bennu. This material is a record of the formation of our solar system, preserved in the vacuum of space for billions of years.
The mission, called OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer), launched on September 8, 2016. It traveled for over two years to reach Bennu, a carbon-rich B-type asteroid about 500 meters in diameter. Bennu was chosen because its dark material is expected to contain organic compounds and water-bearing minerals—the ingredients for life. After mapping the surprisingly rugged surface, the mission team selected a small, relatively clear site named "Nightingale" for sample collection.
A risky maneuver pays off
The sample collection on October 20, 2020, was a high-stakes event over 320 million kilometers from Earth. The OSIRIS-REx spacecraft executed a maneuver called "Touch-And-Go" (TAG). It descended slowly and extended a 3-meter-long robotic arm. The collection head at the end of the arm made contact with Bennu’s surface for approximately six seconds. In that brief window, it fired a burst of nitrogen gas, which fluidized the surface material and pushed it into the collector.
The maneuver worked better than expected. Images showed so much material had been collected that rocks were jamming the collector head's seal, allowing some particles to leak into space. To prevent further loss, mission controllers canceled other planned measurements and quickly stowed the sample head inside the return capsule. The spacecraft began its two-year journey back to Earth on May 10, 2021. The final sample weighed 121.6 grams, more than double the mission's 60-gram science goal. Initial analysis of the dark, crumbly material revealed it contains carbon—nearly 5% by weight—and contains water within clay minerals.