TY - JOUR
T1 - Introduction to the Special Issue
T2 - Exploration of the Activity of Asteroid (101955) Bennu
AU - Hergenrother, C. W.
AU - Adam, C. D.
AU - Chesley, S. R.
AU - Lauretta, D. S.
N1 - Funding Information:
We are grateful to the entire OSIRIS‐REx Team for making the encounter with Bennu possible. We thank everyone who has contributed to the “Exploration of the Activity of the Active Asteroid (101955) Bennu” special issue. This material is based upon work supported by NASA under Contract NNM10AA11C issued through the New Frontiers Program. A portion of this work was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Funding Information:
We are grateful to the entire OSIRIS-REx Team for making the encounter with Bennu possible. We thank everyone who has contributed to the ?Exploration of the Activity of the Active Asteroid (101955) Bennu? special issue. This material is based upon work supported by NASA under Contract NNM10AA11C issued through the New Frontiers Program. A portion of this work was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Publisher Copyright:
©2020. The Authors.
PY - 2020/9/1
Y1 - 2020/9/1
N2 - Near-Earth asteroid (101955) Bennu is an active asteroid experiencing mass loss. The activity manifests itself in the form of ejection events emitting up to hundreds of millimeter- to centimeter-scale particles. The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer spacecraft monitored particle activity for a 10-month period that included Bennu's perihelion and aphelion. Novel and classical methods were utilized to detect the particles and characterize their orbital and physical properties. Roughly 30% of the observed particle mass escaped to heliocentric orbit. A majority of particles fell back onto the surface of Bennu after ejection, with the longest-lived particle surviving for 6 days on a temporary orbit. Particle ejection events appear to preferentially take place in the afternoon and evening and from low latitudes, although they can occur at any time or latitude. The reaccumulation of material is biased toward low latitudes resulting in the possible in-fill of craters and growth of Bennu's equatorial bulge. Of the potential mechanisms behind this activity that were investigated in focused studies, meteoroid impacts, thermal fracturing, and ricochet—but not water ice sublimation—were found to be consistent with observations. While phyllosilicate dehydration was not investigated with a focused study, it remains a possible mechanism. These mechanisms are not unique to Bennu, suggesting that many near-Earth asteroids may exhibit activity that has gone undetected thus far. Spacecraft missions with wide-field imagers are encouraged to further characterize this phenomenon.
AB - Near-Earth asteroid (101955) Bennu is an active asteroid experiencing mass loss. The activity manifests itself in the form of ejection events emitting up to hundreds of millimeter- to centimeter-scale particles. The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer spacecraft monitored particle activity for a 10-month period that included Bennu's perihelion and aphelion. Novel and classical methods were utilized to detect the particles and characterize their orbital and physical properties. Roughly 30% of the observed particle mass escaped to heliocentric orbit. A majority of particles fell back onto the surface of Bennu after ejection, with the longest-lived particle surviving for 6 days on a temporary orbit. Particle ejection events appear to preferentially take place in the afternoon and evening and from low latitudes, although they can occur at any time or latitude. The reaccumulation of material is biased toward low latitudes resulting in the possible in-fill of craters and growth of Bennu's equatorial bulge. Of the potential mechanisms behind this activity that were investigated in focused studies, meteoroid impacts, thermal fracturing, and ricochet—but not water ice sublimation—were found to be consistent with observations. While phyllosilicate dehydration was not investigated with a focused study, it remains a possible mechanism. These mechanisms are not unique to Bennu, suggesting that many near-Earth asteroids may exhibit activity that has gone undetected thus far. Spacecraft missions with wide-field imagers are encouraged to further characterize this phenomenon.
UR - http://www.scopus.com/inward/record.url?scp=85091652947&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85091652947&partnerID=8YFLogxK
U2 - 10.1029/2020JE006549
DO - 10.1029/2020JE006549
M3 - Article
AN - SCOPUS:85091652947
VL - 125
JO - Journal of Geophysical Research: Planets
JF - Journal of Geophysical Research: Planets
SN - 2169-9097
IS - 9
M1 - e2020JE006549
ER -