Every day, thousands of small rocks — dust grain- to pebble-sized — cross paths with Earth’s atmosphere and burn up. More organized collisions, known as meteor showers, are visible to us when the planet passes through whole clouds of rocky debris.
These fragments were long thought to come strictly from comets whose crusts had been heated by the Sun and cracked open. But early in 2019, NASA’s OSIRIS-Rex spacecraft (short for Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) captured images from the near-Earth asteroid Bennu that flipped that line of thinking on its head.
The images showed small bits of rock launching off the asteroid’s surface. Some of the rock fell back to the surface and some went into orbit around Bennu for several days, but about 30 percent was ejected with enough speed that its pieces escaped the asteroid’s gravity and began to orbit around the Sun.
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