More chips off of Asteroid (4) Vesta: Characterization of eight Vestoids and their HED meteorite analogs

Abstract

Vestoids are generally considered to be fragments from Asteroid (4) Vesta that were ejected by past collisions that document Vesta's collisional history. Dynamical Vestoids are defined by their spatial proximity with Vesta (Zappala et al., 1995;Nesvorny et al., 2012). Taxonomic Vestoids are defined as V-type asteroids that have a photometric, visible-wavelength spectral, or other observational relationship with Vesta (Tholen, 1984; Bus and Binzel, 2002; Carvano et al., 2010). We define 'genetic Vestoids' as V-type asteroids that are probable fragments ejected from (4) Vesta based on the supporting combination of dynamical, near-infrared (NIR) spectral, and taxonomic evidence. NIR reflectance spectroscopy is one of the primary ground-based techniques to constrain an asteroid's major surface mineralogy (Burns, 1993a). Despite the reasonable likelihood that many dynamical and taxonomic Vestoids likely originate from Vesta, ambiguity exists concerning the fraction of these populations that are from Vesta as compared to the fraction of asteroids that might not be related to Vesta.Currently, one of the most robust techniques to identify the genetic Vestoid population is through NIR reflectance spectroscopy from ~0.7-2.5 µm. The derivation of spectral band parameters, and the comparison of those band parameters with those from representative samples from the Howardite-Eucrite-Diogenite (HED) meteorite types, allows a direct comparison of their primary mineralogies. Establishing tighter constraints on the genetic Vestoid population will better inform mass estimates for the current population of probable Vestoids, will provide more accurate orbital information of Vestoid migration through time that will assist dynamical models, and will constrain the Icarus, accepted for publication, August 12, 2014 3 overall current abundance of basaltic material in the main asteroid belt (Moskovitz et al., 2008).This work reports high-quality NIR spectra, and their respective interpretations, for eight V p -type asteroids, as defined by Carvano et al. (2010), that were observed at the

Basalt or Not? Near-infrared Spectra, Surface Mineralogical Estimates, and Meteorite Analogs for 33 Vp-type Asteroids

“…Evidence of the remaining basaltic asteroid population beyond (4) Vesta lies with the "Vestoids," which are posited as ejected fragments from Vesta's surface (Hardersen et al 2014, and references therein). These Vestoids are defined using dynamical, taxonomic, mineralogical, and/or meteoritic lines of reasoning, although most potential Vestoids are still dynamically and taxonomically classified as V-type asteroids (Tholen 1984;Zappala et al 1995;Bus & Binzel 2002;Hasselmann et al 2012;Nesvorny 2015).…”

“…Recent work has been attempting to better define the basalt that resides throughout the main belt (Vilas et al 2000;Burbine et al 2001;Kelley et al 2003;Cochran et al 2004;Duffard et al 2006;Moskovitz et al 2008a;Nesvorny et al 2008;Duffard & Roig 2009;Lim et al 2011;Mayne et al 2011;Reddy et al 2011;Hardersen et al 2014Hardersen et al , 2015Leith et al 2017). A larger abundance of V-type asteroids has been identified and classified, which includes a tantalizing collection of possible non-Vesta-related basaltic asteroids (Hasselmann et al 2012;Mainzer et al 2012).…”

“…A larger abundance of V-type asteroids has been identified and classified, which includes a tantalizing collection of possible non-Vesta-related basaltic asteroids (Hasselmann et al 2012;Mainzer et al 2012). Increasing numbers of Vestoids are being characterized that have analogs within the HED suite of basaltic achondrites (Hardersen et al 2014(Hardersen et al , 2015, and references therein). However, no other outer-belt basaltic asteroids have yet been identified.…”

“…The present work builds upon, and expands, the nearinfrared (NIR: 0.7 to 2.5 μm) spectral and mineralogical characterization of the V p taxonomic class of asteroids (Carvano et al 2010), which began with the work of Hardersen et al (2014Hardersen et al ( , 2015. The primary goals of this research are to: (1) identify those inner-belt V p asteroids that have a significant likelihood of having a basaltic surface composition and deriving from (4) Vesta (as Vestoids), (2) better constrain the abundance and distribution of outer-belt basaltic asteroids, and (3) test the predictive ability of the V p taxonomic class to accurately identify basaltic asteroids.…”

“…The above goals will be accomplished by: (1) visually inspecting asteroid NIR spectra and identifying those that are consistent with NIR spectra of HED meteorites, (2) using a three-tiered test to determine those V p asteroids that exhibit NIR spectral and mineralogical properties consistent with a basaltic mineralogy and HED meteorite analogs, (3) constraining the surface mineralogy and potential meteorite analogs for the non-basaltic V p asteroids, and (4) combining the results from Hardersen et al (2014Hardersen et al ( , 2015 with this work to estimate the success rate of the V p taxonomy in predicting a basaltic surface mineralogy and composition.…”