TY - JOUR
T1 - Hungaria asteroid region telescopic spectral survey (HARTSS) I
T2 - Stony asteroids abundant in the Hungaria background population
AU - Lucas, Michael P.
AU - Emery, Joshua P.
AU - Pinilla-Alonso, Noemi
AU - Lindsay, Sean S.
AU - Lorenzi, Vania
N1 - Funding Information:
We are grateful to Bobby Bus, Vishnu Reddy, and Juan Sanchez for helpful discussions regarding this project. We are obliged to Driss Takir, Richard Cartwright, and Richard Ness for contributing observing time. We thank Bill Bottke and David Nesvorný for providing proper orbital elements for Hungaria family members. We also thank Tasha Dunn and an anonymous reviewer for their insightful comments, which helped to improve the manuscript. We appreciate continued observing time at the IRTF to carry out HARTSS. MPL, JPE, and NP-A are visiting astronomers at the IRTF, which is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration (NASA). We acknowledge the Fundación Galileo Galilei (FGG), a Spanish non-profit institution constituted by the Italian Institute of Astrophysics (INAF), for awarding observing time at the TNG. We thank IRTF and TNG Telescope Operators for their assistance. Part of the data utilized in this publication were obtained and made available by The MIT-UH-IRTF Joint Campaign for NEO Reconnaissance, we appreciate Brian Burt for providing observational circumstances for these spectral data. The MIT component of this work is supported by NASA grant 09-NEOO009-0001, and by the National Science Foundation under grants Nos. 0506716 and 0907766. Support for this work was provided by a NASA Earth and Space Sciences Fellowship (NESSF) to JPE and MPL, grant number NNX13AO69H. MPL is grateful to the M.D. Anderson Cancer Center, Houston, TX.
Publisher Copyright:
© 2016 Elsevier Inc.
PY - 2017/7/15
Y1 - 2017/7/15
N2 - The Hungaria asteroids remain as survivors of late giant planet migration that destabilized a now extinct inner portion of the primordial asteroid belt and left in its wake the current resonance structure of the Main Belt. In this scenario, the Hungaria region represents a “purgatory” for the closest, preserved samples of the asteroidal material from which the terrestrial planets accreted. Deciphering the surface composition of these unique samples may provide constraints on the nature of the primordial building blocks of the terrestrial planets. We have undertaken an observational campaign entitled the Hungaria Asteroid Region Telescopic Spectral Survey (HARTSS) to record near-infrared (NIR) reflectance spectra in order to characterize their taxonomy, surface mineralogy, and potential meteorite analogs. The overall objective of HARTSS is to evaluate the compositional diversity of asteroids located throughout the Hungaria region. This region harbors a collisional family of Xe-type asteroids, which are situated among a background (i.e., non-family) of predominantly S-complex asteroids. In order to assess the compositional diversity of the Hungaria region, we have targeted background objects during Phase I of HARTSS. Collisional family members likely reflect the composition of one original homogeneous parent body, so we have largely avoided them in this phase. We have employed NIR instruments at two ground-based telescope facilities: the NASA Infrared Telescope Facility (IRTF), and the Telescopio Nazionale Galileo (TNG). Our data set includes the NIR spectra of 42 Hungaria asteroids (36 background; 6 family). We find that stony S-complex asteroids dominate the Hungaria background population (29/36 objects; ∼80%). C-complex asteroids are uncommon (2/42; ∼5%) within the Hungaria region. Background S-complex objects exhibit considerable spectral diversity as band parameter measurements of diagnostic absorption features near 1- and 2-µm indicate that several different S-subtypes are represented therein, which translates to a variety of surface compositions. We identify the Gaffey S-subtype (Gaffey et al. [1993]. Icarus 106, 573–602) and potential meteorite analogs for 24 of these S-complex background asteroids. Additionally, we estimate the olivine and orthopyroxene mineralogy for 18 of these objects using spectral band parameter analysis established from laboratory-based studies of ordinary chondrite meteorites. Nine of the asteroids have band parameters that are not consistent with ordinary chondrites. We compared these to the band parameters measured from laboratory VIS+NIR spectra of six primitive achondrite (acapulcoite-lodranite) meteorites. These comparisons suggest that two main meteorite groups are represented among the Hungaria background asteroids: unmelted, nebular L- (and possibly LL-ordinary chondrites), and partially-melted primitive achondrites of the acapulcoite-lodranite meteorite clan. Our results suggest a source region for L chondrite like material from within the Hungarias, with delivery to Earth via leakage from the inner boundary of the Hungaria region. H chondrite like mineralogies appear to be absent from the Hungaria background asteroids. We therefore conclude that the Hungaria region is not a source for H chondrite meteorites. Seven Hungaria background asteroids have spectral band parameters consistent with partially-melted primitive achondrites, but the probable source region of the acapulcoite-lodranite parent body remains inconclusive. If the proposed connection with the Hungaria family to fully-melted enstatite achondrite meteorites (i.e., aubrites) is accurate (Gaffey et al. [1992]. Icarus 100, 95–109; Kelley and Gaffey [2002]. Meteorit. Planet. Sci. 37, 1815–1827), then asteroids in the Hungaria region exhibit a full range of petrologic evolution: from nebular, unmelted ordinary chondrites, through partially-melted primitive achondrites, to fully-melted igneous aubrite meteorites.
AB - The Hungaria asteroids remain as survivors of late giant planet migration that destabilized a now extinct inner portion of the primordial asteroid belt and left in its wake the current resonance structure of the Main Belt. In this scenario, the Hungaria region represents a “purgatory” for the closest, preserved samples of the asteroidal material from which the terrestrial planets accreted. Deciphering the surface composition of these unique samples may provide constraints on the nature of the primordial building blocks of the terrestrial planets. We have undertaken an observational campaign entitled the Hungaria Asteroid Region Telescopic Spectral Survey (HARTSS) to record near-infrared (NIR) reflectance spectra in order to characterize their taxonomy, surface mineralogy, and potential meteorite analogs. The overall objective of HARTSS is to evaluate the compositional diversity of asteroids located throughout the Hungaria region. This region harbors a collisional family of Xe-type asteroids, which are situated among a background (i.e., non-family) of predominantly S-complex asteroids. In order to assess the compositional diversity of the Hungaria region, we have targeted background objects during Phase I of HARTSS. Collisional family members likely reflect the composition of one original homogeneous parent body, so we have largely avoided them in this phase. We have employed NIR instruments at two ground-based telescope facilities: the NASA Infrared Telescope Facility (IRTF), and the Telescopio Nazionale Galileo (TNG). Our data set includes the NIR spectra of 42 Hungaria asteroids (36 background; 6 family). We find that stony S-complex asteroids dominate the Hungaria background population (29/36 objects; ∼80%). C-complex asteroids are uncommon (2/42; ∼5%) within the Hungaria region. Background S-complex objects exhibit considerable spectral diversity as band parameter measurements of diagnostic absorption features near 1- and 2-µm indicate that several different S-subtypes are represented therein, which translates to a variety of surface compositions. We identify the Gaffey S-subtype (Gaffey et al. [1993]. Icarus 106, 573–602) and potential meteorite analogs for 24 of these S-complex background asteroids. Additionally, we estimate the olivine and orthopyroxene mineralogy for 18 of these objects using spectral band parameter analysis established from laboratory-based studies of ordinary chondrite meteorites. Nine of the asteroids have band parameters that are not consistent with ordinary chondrites. We compared these to the band parameters measured from laboratory VIS+NIR spectra of six primitive achondrite (acapulcoite-lodranite) meteorites. These comparisons suggest that two main meteorite groups are represented among the Hungaria background asteroids: unmelted, nebular L- (and possibly LL-ordinary chondrites), and partially-melted primitive achondrites of the acapulcoite-lodranite meteorite clan. Our results suggest a source region for L chondrite like material from within the Hungarias, with delivery to Earth via leakage from the inner boundary of the Hungaria region. H chondrite like mineralogies appear to be absent from the Hungaria background asteroids. We therefore conclude that the Hungaria region is not a source for H chondrite meteorites. Seven Hungaria background asteroids have spectral band parameters consistent with partially-melted primitive achondrites, but the probable source region of the acapulcoite-lodranite parent body remains inconclusive. If the proposed connection with the Hungaria family to fully-melted enstatite achondrite meteorites (i.e., aubrites) is accurate (Gaffey et al. [1992]. Icarus 100, 95–109; Kelley and Gaffey [2002]. Meteorit. Planet. Sci. 37, 1815–1827), then asteroids in the Hungaria region exhibit a full range of petrologic evolution: from nebular, unmelted ordinary chondrites, through partially-melted primitive achondrites, to fully-melted igneous aubrite meteorites.
KW - Asteroids
KW - Aubrites, Asteroid taxonomy
KW - H chondrites, L chondrites, LL chondrites
KW - Hungaria asteroids
KW - Lodranites
KW - Near-infrared spectroscopy
KW - Ordinary chondrites
KW - Primitive achondrites, Acapulcoites
KW - Surface mineralogy
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U2 - 10.1016/j.icarus.2016.11.002
DO - 10.1016/j.icarus.2016.11.002
M3 - Article
AN - SCOPUS:85017615552
SN - 0019-1035
VL - 291
SP - 268
EP - 287
JO - Icarus
JF - Icarus
ER -