Bunburra Rockhole: Exploring the geology of a new differentiated asteroid

Abstract

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The mineralogy, petrology, and composition of anomalous eucrite Emmaville

“…; Benedix et al. ) in which there is evidence of some isotopic heterogeneity, but none of the various fractions have a HED Δ 17 O composition. Although the various fractions of Emmaville are slightly displaced to lighter Δ 17 O values than Bunburra Rockhole there would appear to be considerable overlap between the two meteorites, based on a comparison of O isotopes between Fig.…”

“…Benedix et al. () suggested that Bunburra Rockhole may be derived from the same parent body as A‐881394. If this interpretation is correct then Emmaville may represent a third sample from this body.…”

“…On a plot of Δ 17 O versus ɛ 54 Cr both A‐881394 and Bunburra Rockhole form a distinct cluster that is fully resolvable from normal eucrites (Benedix et al. ). Although the ɛ 54 Cr composition of Emmaville and EET 92023 have not yet been determined, on the basis of their similar oxygen isotope compositions it seems possible that all four samples (Bunburra Rockhole, A‐881394, Emmaville, and EET 92023) are derived from an isotopically distinct HED‐like parent.…”

Can Formulas Derived From Pyroxenes and/or HEDs Be Used to Determine the Mineralogies of V‐Type Asteroids?

“…Vesta was also one of the targets of the Dawn spacecraft mission (Russell et al, ), whose measurements were also consistent with a linkage with HEDs (e.g., McSween et al, ). However, some HEDs have distinctly different oxygen isotope values from typical HED values (e.g., Benedix et al, ; Scott et al, ) implying more than one Vesta‐like asteroid formed in the solar system. Hardersen et al () has determined the pyroxene mineralogies of approximately 30 V‐type asteroids in the inner and outer belt to test their mineralogical relationship with Vesta.…”

Mineralogical Criteria for the Parent Asteroid of the “Carbonaceous” Achondrite NWA 6704

“…These variations in stable isotopes that are evident among the anomalous achondrites further reinforce the distinction from the HEDs (Greenwood et al 2017). Previous work has determined a subset of the achondrites with anomalous oxygen isotope values which includes the following: Ibitira (eucrite) and NWA 011 (ungrouped achondrite; Yamaguchi et al 2002), Pasamonte (eucrite; Weichert et al 2004;Greenwood et al 2005;Scott et al 2009), Emmaville (eucrite; Greenwood et al 2013), Asuka 881394 (eucrite; Scott et al 2009), and Bunburra Rockhole (eucrite; Bland et al 2009;Benedix et al 2017). The oxygen isotopic diversity exposes variations in oxidizing environments on corresponding parent objects, and these variations among the sampled anomalous achondrites could be in turn revealing a suite of parental sources in the solar system.…”