DART mission unveils origin of battered space rock Dimorphos.

NASA's DART mission successfully tested our ability to defend Earth from a threatening asteroid by nudging it out of harm's way. The mission also revealed that the asteroid Dimorphos didn't form on its own but rather as a ring of material flung off from its larger parent, Didymos. The researchers propose that the YORP effect triggered avalanches on the surface of Didymos, which were then flung away from the parent asteroid due to the extreme angular momentum. That material then gathered in a ring surrounding Didymos, eventually forming Dimorphos.