Infrared sensors on the ground detected the heat signature of the OSIRIS-REx spacecraft’s sample-return capsule when it slammed into the atmosphere at more than 45,000 km/h (27,650 mph), at 8:42 a.m. MDT today. The 46 kg (101 lbs.) capsule was dropped off by its much larger OSIRIS-REx mother ship as that spacecraft went whizzing briefly by Earth. The capsule hit the air off the coast of California, aiming for a parachute landing in the Department of Defense’s Utah Test and Training Range southwest of Salt Lake City. Even before the capsule landed, four search helicopters scrambled to meet it, and the people at NASA waited anxiously to hear that it had returned safely.

It had. The capsule thumped down at 8:55 a.m. MDT and the helicopter crews scooped it up and whisked it to a …