On 20 October, after several years of patient study of its enigmatic target, NASA's $800 million Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) spacecraft will finally stretch out its robotic arm, swoop to the surface of the near-Earth asteroid Bennu, and sweep up some dust and pebbles. If successful, OSIRIS-REx could steal away with up to 1 kilogram of carbon-rich material from the dawn of the Solar System for return to Earth in 2023. Bennu has yielded surprises since the spacecraft's arrival in 2018. The 500-meter-wide asteroid was not smooth, as expected, but studded with more than 200 large boulders that could upset the sampling maneuver. The boulders, however, contain a prize: veins of carbonate minerals thicker than your hand. These minerals suggest Bennu's parent, an ancient planetesimal, had liquid water flowing throughout its body during the Solar System's earliest days.