of the construction time required and orbital dynamics, a launch date of October 2028 was proposed. On January 6, 2019, the OSIRIS-REx mission first observed episodes of particle ejection from 101955 Bennu shortly after entering orbit around the near-Earth asteroid, leading it to be newly classified as an active asteroid and marking the first time that asteroid activity had been observed up close by a spacecraft. It has since observed at least 10 other such events. The scale of these observed mass loss events is much smaller than those previously observed at other active asteroids by telescopes, indicating that there is a continuum of mass loss event magnitudes at active asteroids. See also Centaur (minor planet) Extinct comet References External links Proper elements of active asteroids at Asteroid Families Portal Henry Hsieh's Main-Belt Comets page has extensive details on Main-belt comets David Jewitt. The Active Asteroids Planetary Society article on MBCs Discussion of possible differences in characteristics of the water in MBCs and other comets YouTube Interview with David Jewitt (discussion on main-belt comets starts around 9 minutes into video) Impact trigger mechanism diagram by David Jewitt Comet-like appearance of (596) Scheila Project T3: Finding Comets in the Asteroid Population New Comet: P/2012 T1 (PANSTARRS) (Remanzacco Observatory : 16 Oct 2012) P/2013 R3: a Main Belt Comet that is breaking apart. J. Licandro New images obtained with the GTC Asteroids Comets