Hungaria asteroid region telescopic spectral survey (HARTSS) I: Stony asteroids abundant in the Hungaria background population

Abstract

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 Scomplex 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), of which 27 were observed during HARTSS (22 at IRTF, 5 at TNG). To complement our data set, we have included previously published NIR spectra of 15 objects, and previously published visible (VIS) spectra of 21 asteroids. 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 3 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 (acapulcoitelodranite) meteorites. These comparisons suggest that two main meteorite groups are represented among the Hungaria background asteroids: unmelted, nebular L-(and possibly LLordinary...

Follow-up observations for the Asteroid Catalog using AKARI Spectroscopic Observations

“…The Bus-DeMeo classification for all the AcuA-spec asteroids was performed in the previous section; however, in addition to the classification data of the AcuA-spec asteroids, all the data in the accepted articles prior to this study, should be utilized to constrain each spectral type asteroid, using the Bus-DeMeo taxonomy from a statistical point of view. Therefore, the Bus-DeMeo classification, for use in this study, was extended to the Lucas et al (2017), and the previous section of this study. 767 asteroids were already classified using the Bus-DeMeo taxaonomy.…”

Study on the asteroidal spin characteristics in the Hungaria region

“…(1727) Mette being a member of the Hungaria region asteroids is identified as a S-type asteroid based on the polarimetric data by Belskaya et al (2017) or a Sw-type asteroid based on the visible and near-infrared reflectance spectral data by Lucas et al (2017). Wisniewski & McMillan (1987) and Prokof'Eva et al (1992)…”

“…Kenos is identified as a Xn/L-type asteroid by Lucas et al (2017) or a Xc-type asteroid by Binzel et al (2019) in the Hungaria region, and its rotation period of 4.188 hr is reported preferentially by Wisniewski et al (1997).…”

“…Hoag is identified as a S-type Hungaria region asteroid by Lucas et al (2017) and its rotation period near 2.37 hr is obtained by Stephens & Warner (2019, 2020b; Warner (2007Warner ( , 2009bWarner ( , 2010bWarner ( , 2014a; Waszczak et al (2015). Utilizing the six apparitions photometric lightcurves provided by Stephens & Warner (2019, 2020b; Warner (2007Warner ( , 2009bWarner ( , 2010bWarner ( , 2014a, in the ALCDEF database, we obtain Hoag's optimal spin pole orientation (𝜆 p = 310 • , 𝛽 p = −79 • ) with the rotation period of 2.3725 ± 0.0001 hr.…”

A survey on Hungaria asteroids involved in mean motion resonances with Mars

“…As a last step of our survey, we investigate possible relationships between dynamical and physical properties of the asteroids belonging to the Hungaria group. There has been a series of measurements (Lucas et al 2017(Lucas et al , 2019 aiming at revealing various physical properties of Hungaria asteroids such as the absolute magnitude, size, shape, and albedo. These measurements are thought to help discover the variety of asteroids, in a broader sense even the properties of the building blocks of the ancient Solar System.…”