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Science. 2019 Dec 6;366(6470). pii: eaay3544. doi: 10.1126/science.aay3544.

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

Author information

1
Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA. lauretta@orex.lpl.arizona.edu chergen@lpl.arizona.edu.
2
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
3
KinetX Aerospace, Simi Valley, CA, USA.
4
Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada.
5
Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA.
6
NASA Goddard Space Flight Center, Greenbelt, MD, USA.
7
Southwest Research Institute, Boulder, CO, USA.
8
Department of Physics, University of Central Florida, Orlando, FL, USA.
9
Department of Geology, Rowan University, Glassboro, NJ, USA.
10
The Centre for Research in Earth and Space Science, York University, Toronto, ON, Canada.
11
Smead Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO, USA.
12
Instituto de Astrofísica de Canarias and Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain.
13
Department of Geosciences, University of Arizona, Tucson, AZ, USA.
14
Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN, USA.
15
Department of Astronomy and Planetary Sciences, Northern Arizona University, Flagstaff, AZ, USA.
16
Department of Aerospace Engineering, University of Maryland, College Park, MD, USA.
17
Smithsonian Institution National Museum of Natural History, Washington, DC, USA.
18
SETI (Search for Extraterrestrial Intelligence) Institute, Mountain View, CA, USA.
19
Planetary Science Institute, Tucson, AZ, USA.
20
Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS (Centre national de la recherche scientifique), Laboratoire Lagrange, Nice, France.
21
London Stereoscopic Company, London, UK.
22
School of Physical Sciences, Open University, Milton Keynes, UK.
23
Institute of Astronomy, Charles University, Prague, Czech Republic.
#
Contributed equally

Abstract

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.

Comment in

PMID:
31806784
DOI:
10.1126/science.aay3544

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