Bibcode
Lucas, Michael P.; Emery, Joshua P.; MacLennan, Eric M.; Pinilla-Alonso, Noemi; Cartwright, Richard J.; Lindsay, Sean S.; Reddy, Vishnu; Sanchez, Juan A.; Thomas, Cristina A.; Lorenzi, V.
Referencia bibliográfica
Icarus, Volume 322, p. 227-250.
Fecha de publicación:
4
2019
Revista
Número de citas
17
Número de citas referidas
16
Descripción
Spectral observations of asteroid family members provide valuable
information regarding parent body interiors, the origin and source
regions of near-Earth asteroids, and the link between meteorites and
their parent bodies. Asteroids of the Hungaria family represent some of
the closest samples to the Earth from a collisional family (∼1.94
AU), permitting observations of smaller family fragments than accessible
for Main Belt families. We have carried out a ground-based observational
campaign entitled Hungaria Asteroid Region Telescopic Spectral Survey
(HARTSS) to record reflectance spectra of these preserved samples from
the inner-most regions of the primordial asteroid belt. During HARTSS
phase one (Lucas et al. (2017). Icarus 291, 268-287) we found that
∼80% of the background population is comprised of stony S-complex
asteroids that exhibit considerable spectral and mineralogical
diversity. In HARTSS phase two, we turn our attention to family members
to determine if the Hungaria collisional family is compositionally
homogeneous or heterogeneous. We use taxonomic classification, geometric
albedo (pv) estimates, and near-infrared (NIR) spectral
properties to infer the composition of the family.
During phase two of HARTSS we acquired NIR spectra of 50 new Hungarias
(19 family; 31 background) with the SpeX spectrograph at NASA's Infrared
Telescope Facility (IRTF) and with the NICS spectrograph at the
Telescopio Nazionale Galileo (TNG). We analyzed X-type spectra for NIR
color indices (0.85-J; J-K), and a subtle ∼0.9 μm absorption
feature that may be attributed to Fe-poor orthopyroxene ± the
sulfide mineral oldhamite. Surviving fragments of an asteroid
collisional family typically exhibit similar taxonomies, albedos, and
spectral properties. Spectral analysis of Hungaria family X-types and
independently calculated WISE albedos for family members (average
pv= 0.403; n = 192) is consistent with this scenario.
Furthermore, about one-fourth of the background population exhibit
similar spectral properties and albedos to family X-types.
Spectral observations of 92 Hungaria region asteroids acquired during
both phases of HARTSS uncover a compositionally-heterogeneous background
population-including two rare olivine-dominated A-types and one apparent
D-type interloper-and spectral homogeneity down to ∼2 km for
collisional family members. Taxonomy, albedos, and spectral properties
indicate that the Hungaria family progenitor was an igneous body that
formed under reduced conditions, and was likely consistent in
composition with the enstatite achondrite (i.e., aubrite) meteorite
group.
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