Spectral and mineralogical characterization of inner main-belt V-type asteroids

Abstract

Context. V-type asteroids in the inner main belt are thought to be genetically related to (4) Vesta as collisional fragments. We investigate their relationship with Vesta observing putative V-type asteroids. Aims. The aim of this work is to observe candidate V-type asteroids, selected in different regions of the inner main belt, to characterize them and hence better understand their relationship with (4) Vesta. Methods. We present new NIR reflectance spectra of 18 V-type candidate asteroids, selected from datasets of possible V-type asteroids. The data were obtained at the 3.6 m Telescopio Nazionale Galileo, covering the spectral range 0.7 to 2.5 μm. We derive spectral parameters from NIR spectra to infer mineralogical information of the observed asteroids. The spectra of these asteroids are examined and compared to those of Howardite-Eucrite-Diogenite meteorites (HED), of which (4) Vesta is believed to be the parent body, and other V-type asteroids observed during previous campaigns. To enlarge the data set and increase the statistical significance of the analysis, we included the data presented in our previous article, obtaining a final data set of 41 V-type asteroids. Results. The V-type asteroids examined here show a higher variability of band parameters with respect to HEDs values, as for (4) Vesta. This result indicates that (4) Vesta and V-type asteroids have mineralogies that are not completely represented in the HEDs collection.Conclusions. An important finding is that some of the observed asteroids show spectral characteristics similar to diogenites, a result that may have relevant implications on their origin. Moreover, most of the diogenitic asteroids are not members of the Vesta classical family.

Surface Composition of Vesta: Issues and Integrated Approach

“…The strength of the bands observed for the Vestoids are much closer to that observed in laboratory studies of meteorites (Binzel and Xu 1993;Hiroi et al 1995;Pieters et al 2006). Marchi et al (2010), Moskovitz et al (2010), andDe Sanctis et al (2011b) investigated several of the small Vestoids using earth-based telescopes and found that their visible slopes are generally redder than that of Vesta and systematically redder than HEDs measured in the laboratory. The observed trend for Vestoids (steeper continuum, stronger absorption bands) is opposite that observed for S-type asteroids (steeper continuum, weaker absorption bands), again suggesting that Vesta and its family of small asteroids is distinctive.…”

“…Telescopic studies measuring the spectral reflectance of both Vesta and V-type asteroids associated with Vesta (Vestoids) have sought evidence of compositional variations across Vesta's surface and among the Vestoids (Gaffey 1997;Vernazza et al 2005;Reddy et al 2010Reddy et al , 2011Carry et al 2010;Duffard et al 2004;Moskovitz et al 2010;De Sanctis et al 2011b). Gaffey (1997) examined spectral variations as a function of longitude as Vesta rotates.…”

Modeling of asteroid spectra – M4AST

“…Cloutis et al (1990) noted that the band separation is a linear function of the BII minimum for orthopyroxenes and that both parameters increase with the iron content. If we refer to the relation obtained by de Sanctis et al (2011), the parameters that we found match their formula y = 0.801 * x − 0.536, where y is the band separation and x is the BII minimum. These parameters corresponds to an iron content of around 40 wt%.…”

“…These parameters corresponds to an iron content of around 40 wt%. However, the laboratory calibrations suggest that the correspondence is true for a number of low aluminum orthopyroxenes but invalid for mixtures of olivine, metal, and both ortho-and clino-pyroxenes (de Sanctis et al 2011). …”

DETECTION OF WIDESPREAD HYDRATED MATERIALS ON VESTA BY THE VIR IMAGING SPECTROMETER ON BOARD THE DAWN MISSION

“…Its spectra are similar to those of howardite, eucrite, and diogenite meteorites (HEDs), so it has been suggested that Vesta is the source of this class of meteorites (Consolmagno & Drake 1977;Takeda 1997;Drake 2001). A family of small, V-type asteroids, the so-called Vestoids, is dynamically associated with Vesta (Binzel & Xu 1993;Duffard et al 2004;Moskovitz et al 2010;De Sanctis et al 2011a, 2011c. Notably, the link between distant Vestoids and HEDs is provided by several V-types observed among nearEarth objects (e.g., Marchi et al 2005).…”