TY - JOUR
T1 - Collisional family structure within the Nysa-Polana complex
AU - Dykhuis, Melissa J.
AU - Greenberg, Richard
N1 - Funding Information:
The authors are grateful to Miroslav Broz and an anonymous reviewer for their comments, which significantly improved the quality of this manuscript. We acknowledge the use of data from the Sloan Digital Sky Survey, and thank the Sloan team and its sponsors (see http://www.sdss.org ). In addition, this publication makes use of data products from the Wide-field Infrared Survey Explorer and NEOWISE, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration . We thank Bill Bottke, Dante Lauretta and the OSIRIS-REx science team for their guidance and advice. In addition, we thank Nathaniel Dykhuis for his assistance with the statistical analysis. MJD was supported by an NSF Graduate Research Fellowship , Award No. DGE-1143953 , with additional support from the OSIRIS-REx Dynamical Evolution Working Group .
Publisher Copyright:
© 2015 Elsevier Inc.
PY - 2015/5/5
Y1 - 2015/5/5
N2 - The Nysa-Polana complex is a group of low-inclination asteroid families in the inner main belt, bounded in semimajor axis by the Mars-crossing region and the Jupiter 3:1 mean-motion resonance. This group is important as the most likely source region for the target of the OSIRIS-REx mission, (101955) Bennu; however, family membership in the region is complicated by the presence of several dynamically overlapping families with a range of surface reflectance properties.The large S-type structure in the region appears to be associated with the parent body (135) Hertha, and displays an (eP, aP) correlation consistent with a collision event near true anomaly of ~180° with ejecta velocity vej~285m/s. The ejecta distribution from a collision with these orbital properties is predicted to have a maximum semimajor axis dispersion of δaej=0.005±0.008AU, which constitutes only a small fraction (7%) of the observed semimajor axis dispersion, the rest of which is attributed to the Yarkovsky effect. The age of the family is inferred from the Yarkovsky dispersion to be 300-50+60My.Objects in a smaller cluster that overlaps the large Hertha family in proper orbital element space have reflectance properties more consistent with the X-type (135) Hertha than the surrounding S-type family. These objects form a distinct Yarkovsky "V" signature in (aP, H) space, consistent with a more recent collision, which appears to also be dynamically connected to (135) Hertha. Production of two families with different reflectance properties from a single parent could result from the partial differentiation of the parent, shock darkening effects, or other causes.The Nysa-Polana complex also contains a low-albedo family associated with (142) Polana (called "New Polana" by Walsh et al. (Walsh, K.J. et al. [2013]. Icarus 225, 283-297)), and two other low-albedo families associated with (495) Eulalia. The second Eulalia family may be a high-aP, low-eP, low-iP component of the first Eulalia family-forming collision, possibly explained by an anisotropic ejection field.
AB - The Nysa-Polana complex is a group of low-inclination asteroid families in the inner main belt, bounded in semimajor axis by the Mars-crossing region and the Jupiter 3:1 mean-motion resonance. This group is important as the most likely source region for the target of the OSIRIS-REx mission, (101955) Bennu; however, family membership in the region is complicated by the presence of several dynamically overlapping families with a range of surface reflectance properties.The large S-type structure in the region appears to be associated with the parent body (135) Hertha, and displays an (eP, aP) correlation consistent with a collision event near true anomaly of ~180° with ejecta velocity vej~285m/s. The ejecta distribution from a collision with these orbital properties is predicted to have a maximum semimajor axis dispersion of δaej=0.005±0.008AU, which constitutes only a small fraction (7%) of the observed semimajor axis dispersion, the rest of which is attributed to the Yarkovsky effect. The age of the family is inferred from the Yarkovsky dispersion to be 300-50+60My.Objects in a smaller cluster that overlaps the large Hertha family in proper orbital element space have reflectance properties more consistent with the X-type (135) Hertha than the surrounding S-type family. These objects form a distinct Yarkovsky "V" signature in (aP, H) space, consistent with a more recent collision, which appears to also be dynamically connected to (135) Hertha. Production of two families with different reflectance properties from a single parent could result from the partial differentiation of the parent, shock darkening effects, or other causes.The Nysa-Polana complex also contains a low-albedo family associated with (142) Polana (called "New Polana" by Walsh et al. (Walsh, K.J. et al. [2013]. Icarus 225, 283-297)), and two other low-albedo families associated with (495) Eulalia. The second Eulalia family may be a high-aP, low-eP, low-iP component of the first Eulalia family-forming collision, possibly explained by an anisotropic ejection field.
KW - Asteroids
KW - Asteroids, Dynamics
KW - Resonances, Orbital
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U2 - 10.1016/j.icarus.2015.01.012
DO - 10.1016/j.icarus.2015.01.012
M3 - Article
AN - SCOPUS:84922970365
VL - 252
SP - 199
EP - 211
JO - Icarus
JF - Icarus
SN - 0019-1035
ER -