Vesta, vestoids, and the HED meteorites: Interconnections and differences based on Dawn Framing Camera observations

Abstract

[1] The Framing Camera (FC) on the Dawn spacecraft provided the first view of 4 Vesta at sufficiently high spatial resolution to enable a detailed correlation of the asteroid's spectral properties with geologic features and with the vestoid (V-type) asteroids and the Howardite-Eucrite-Diogenite (HED) class of meteorites, both of which are believed to originate on Vesta. We combine a spectral analysis of the basin with visible and near-IR spectroscopy of vestoids and with archived data over the same spectral range for HED meteorites. The vestoids are only slightly more akin to the Rheasilvia basin than to Vesta as a whole, suggesting that the crustal material ejected is a well-mixed collection of eucritic and diogenitic materials. The basin itself is more diogenitic, implying Vesta is differentiated and the impact that created Rheasilvia uncovered a mineralogically distinct layer. The Rheasilvia basin exhibits a larger range in pyroxene band strengths than Vesta as a whole, further implying that the basin offers a view into a complex, differentiated protoplanet. The discrepancy between the spectral properties of the HED meteorites and Vesta, in particular the meteorites' deeper pyroxene absorption band and the redder color of the vestoids, can be explained by the abundance of smaller particles on Vesta and by the addition of low-albedo exogenous particles to its surface, which in turn are due to its larger gravity and longer exposure time to impact processing. Solar phase effects are slight and do not explain the spectral discrepancies between the HEDs, Vesta, and the vestoids.

A deep crust–mantle boundary in the asteroid 4 Vesta

“…If so, then olivine-rich deeper rocks excavated during the second impact should still be prominently visible among the vestoids. This is definitely not the case, as all of them have 1 spectral signatures similar to eucrites, diogenites or a mixture of both [18][19][20] . Once again, those observations are at odds with the idea of an approximately 30-40-km-thick crust.…”

Data‐driven taxonomy matching of asteroid and meteorite

“…The in situ analysis by the Dawn mission confirmed this link and provided further insights on the relations (Buratti et al. ). Another famous link is seen between S‐type asteroids and ordinary chondrite meteorites, which had been predicted for long (Hiroi et al.…”

“…One of the earliest links between asteroids and meteorites is seen for 4 Vesta (V-type asteroids) and howardite-eucrite-diogenite (HED) meteorites (McCord et al 1970). The in situ analysis by the Dawn mission confirmed this link and provided further insights on the relations (Buratti et al 2013). Another famous link is seen between S-type asteroids and ordinary chondrite meteorites, which had been predicted for long (Hiroi et al 1993;Chapman 1996), and was confirmed by the analysis of the sample taken from Itokawa by the Hayabusa mission (Nakamura et al 2011); however, the spectra of Itokawa are different from existing ordinary chondrites, and the discrepancy has been thought to be caused by space weathering (Noguchi et al 2011).…”

Three-dimensional spectral analysis of compositional heterogeneity at Arruntia crater on (4) Vesta using Dawn FC

“…The spectral slope in the visible wavelength range of FC color data, generally defined by a ratio of reflectance values at 0.43 and 0.75 µm (0.43/0.75 µm), has been used elsewhere (e.g., Reddy et al, 2012b;Buratti et al, 2013;Le Corre et al, 2013;Schaefer et al, 2014) to analyze composition and surface properties of Vesta. The spectral slope has also widely implemented in comparative studies of Vesta, Vestoids, and HED meteorites (e.g., Buratti et al, 2013;Hicks et al, 2014;Hiroi and Pieters, 1998;Burbine et al, 2001). Computation of the slope from spectra normalized to a particular wavelength is typical for ground-based telescopic data (e.g., Luu and Jewitt, 1990;Bus and Binzel, 2002;Hicks et al, 2014).…”