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Episodes of particle ejection from the surface of the active asteroid (101955) Bennu.

Dante S LaurettaCarl W HergenrotherSteven R ChesleyJason M LeonardJohn Y PelgriftCoralie D AdamM Al AsadP G AntreasianRonald-Louis BallouzK J BeckerCarina A BennettB J BosWilliam F BottkeM BrozovićHumberto CampinsHarold C ConnollyMichael G DalyA B DavisJulia de LeónDaniella N DellaGiustinaC Y Drouet d'AubignyJason P DworkinJoshua P EmeryD FarnocchiaDaniel P GlavinDathon R GolishChristine M HartzellR A JacobsonErica R JawinPeter JenniskensJ N KiddErik J Lessac-ChenenJian-Yang LiGuy LibourelJ LicandroA J LiounisC K MaleszewskiC ManzoniB MayL K McCarthyJ W McMahonPatrick MichelJ L MolaroMichael MoreauDerek S NelsonW M OwenBashar RizkH L RoperB RozitisEric M SahrDaniel J ScheeresJ A SeabrookSanford H SelznickY TakahashiF ThuilletP TricaricoD VokrouhlickýC W V Wolner
Published in: Science (New York, N.Y.) (2020)
Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.
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