Shortly after NASA’s OSIRIS-REx spacecraft arrived at asteroid Bennu, an unexpected discovery by the mission’s science team revealed that the asteroid could be active, or consistently discharging particles into space. The ongoing examination of Bennu—and its sample that will eventually be returned to Earth—could potentially shed light on why this intriguing phenomenon is occurring.
Source:
https://phys.org/news/2019-12-osiris-rex-mission-bennu-mysterious-particle.html