TY - JOUR
T1 - Same family, different neighborhoods
T2 - Visible near-infrared (0.7–2.45 μm) spectral distinctions of D-type asteroids at different heliocentric distances
AU - Gartrelle, Gordon M.
AU - Hardersen, Paul S.
AU - Izawa, Matthew R.M.
AU - Nowinski, Matthew C.
N1 - Funding Information:
The authors would like to express our deep gratitude to Francesca DeMeo and Joshua Emery who generously provided their IRTF D-type spectra and invaluable guidance to improve our understanding of D-types and Jovian Trojans. We would also like to thank Paul Abell, Wayne Barkhouse, and Michael Gaffey for their insightfully honest critical feedback. We greatly appreciate the technical input and editorial support of Brian Burt, Ron Fevig, Szilard Gyalay, Aur?lie Guilbert-Lepoutre, Tomoki Nakamura, Ted Roush, and Bin Yang. Special thanks to Maria Antonella Barucci, Rick Binzel, Tom Burbine, Deborah Domingue, and Faith Vilas for their inspiration and mentoring. We are also immensely grateful to James Casler, recently retired from the University of North Dakota, for his creative leadership, sincere support, and executive oversight. Finally, we thank our anonymous peer reviewers for their constructive comments and candor. This study was performed using joint-user facilities of the Institute for Planetary Materials, Okayama University. We express deep appreciation and thanks to the Institute for their gracious hospitality, support, and cooperation. Finally, we are immensely grateful to the entire team at NASA/IRTF for their help, and are especially thankful for the contribution of the people of Hawaii who offered use of their sacred land from which we observed the heavens.
Publisher Copyright:
© 2021 Elsevier Inc.
PY - 2021/7/15
Y1 - 2021/7/15
N2 - D-type asteroids represent a complex mystery related to the accretional history, composition, and dynamical migration of Outer Solar System objects. These spectrally featureless bodies have revealed few clues while raising many questions over four decades. D-types are dark, difficult to observe and perhaps contain unaltered primordial material. D-type asteroids are abundant in the outer belt, dominant in the Jupiter Trojans, and rare in the inner belt as well as near Earth space. Material spectrally similar to D-types is pervasive on other outer solar system bodies as well. The appearance of dark, spectrally red material in multiple classes of small bodies suggests some unknown geochemical and/or evolutionary connection(s) may exist between them. Our investigation focused on the visible near-infrared (VNIR) (0.7–2.45 μm) spectral distinctions of D-types based on heliocentric location. Twenty-five newly acquired spectra from NASA's Infrared Telescope Facility (IRTF) plus sixty-one IRTF VNIR spectra from the literature were combined into a single database and extensively analyzed with multiple orbital, observational, and spectral variables included in the examination. Twelve of the newly acquired spectra had not been imaged previously at IRTF. Pearson's correlation, simple and multiple regression, slope analysis, Monte Carlo modeling, as well as Principal Component Analysis (PCA) determined D-types show increased reddening with decreasing distance, with the segment from 1.5–2.45 μm, driving the overall trend for the full slope. Principal components show strong connection to the 0.7–1.35 μm slope and inclination of D-type Jupiter Trojans. Principal component combinations, magnitudes, and positive/negative direction relate strongly to both observed and derived differences in the D-type L4 and L5 Trojan population. The L5 population is less evolved spectrally and dynamically than L4 counterparts perhaps due to lower dynamical instabilities inside the L4 cloud.
AB - D-type asteroids represent a complex mystery related to the accretional history, composition, and dynamical migration of Outer Solar System objects. These spectrally featureless bodies have revealed few clues while raising many questions over four decades. D-types are dark, difficult to observe and perhaps contain unaltered primordial material. D-type asteroids are abundant in the outer belt, dominant in the Jupiter Trojans, and rare in the inner belt as well as near Earth space. Material spectrally similar to D-types is pervasive on other outer solar system bodies as well. The appearance of dark, spectrally red material in multiple classes of small bodies suggests some unknown geochemical and/or evolutionary connection(s) may exist between them. Our investigation focused on the visible near-infrared (VNIR) (0.7–2.45 μm) spectral distinctions of D-types based on heliocentric location. Twenty-five newly acquired spectra from NASA's Infrared Telescope Facility (IRTF) plus sixty-one IRTF VNIR spectra from the literature were combined into a single database and extensively analyzed with multiple orbital, observational, and spectral variables included in the examination. Twelve of the newly acquired spectra had not been imaged previously at IRTF. Pearson's correlation, simple and multiple regression, slope analysis, Monte Carlo modeling, as well as Principal Component Analysis (PCA) determined D-types show increased reddening with decreasing distance, with the segment from 1.5–2.45 μm, driving the overall trend for the full slope. Principal components show strong connection to the 0.7–1.35 μm slope and inclination of D-type Jupiter Trojans. Principal component combinations, magnitudes, and positive/negative direction relate strongly to both observed and derived differences in the D-type L4 and L5 Trojan population. The L5 population is less evolved spectrally and dynamically than L4 counterparts perhaps due to lower dynamical instabilities inside the L4 cloud.
KW - Asteroids
KW - D-type asteroids
KW - Jupiter Trojans
KW - Spectrally featureless asteroids
KW - VNIR spectroscopy
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U2 - 10.1016/j.icarus.2020.114295
DO - 10.1016/j.icarus.2020.114295
M3 - Article
AN - SCOPUS:85105000862
VL - 363
JO - Icarus
JF - Icarus
SN - 0019-1035
M1 - 114295
ER -