New research suggests the asteroid Didymos spins so rapidly it casts off a stream of rocks and dust, and that the phenomenon may be the origin of its moonlet, Dimorphos, which was redirected by NASA's DART spacecraft last October as an initial test of a proposed planetary defense system. Right now the work is based almost entirely on remote observations gathered before the DART mission. "It's a good place to start, and that's all we can do," said University of Arizona Regents Professor of Planetary Sciences Dante Lauretta.