^1,2Timothy Gregory,¹Katherine Helen Joy,³Stanislav Strekopytov,¹Natalie Mary Curran
Meteoritics & Planetary Science (in Press) Link to Article [10.1111/maps.12782]
¹School of Earth and Environmental Science, University of Manchester, Manchester, UK
²School of Earth Sciences, University of Bristol, Bristol, UK
³Imaging and Analysis Centre, The Natural History Museum, London, UK
Published by arrangement with John Wiley & Sons

The howardite-eucrite-diogenite (HED) clan of meteorites, which most likely originate from the asteroid Vesta, provide an opportunity to combine in-depth sample analysis with the comprehensive remote-sensing data set from NASA’s recent Dawn mission. Miller Range (MIL) 11100, an Antarctic howardite, contains diverse rock and mineral fragments from common HED lithologies (diogenites, cumulate eucrites, and basaltic eucrites). It also contains a rare pyroxferroite-bearing lithology—not recognized in HED until recently—and rare Mg-rich (Fo86-91) olivine crystals that possibly represent material excavated from the Vestan mantle. Clast components underwent different histories of thermal and impact metamorphism before being incorporated into this sample, reflecting the diversity in geological histories experienced by different parts of Vesta. The bulk chemical composition and petrography of MIL 11100 suggest that it is akin to the fragmental howardite meteorites. The strong lithological heterogeneity across this sample suggests that at least some parts of the Vestan regolith show heterogeneity on the mm-scale. We combine the outcomes of this study with data from NASA’s Dawn mission and hypothesize on possible source regions for this meteorite on the surface of Vesta.

¹N. G. Rudraswami,¹K. Reshma,¹M. Shyam Prasad
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12783]
¹National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa, India
Published by arrangement with John Wiley & Sons

Micrometeorites provide a large range of samples sourced from a wide variety of planetary materials, thereby providing a scope for expanding the known inventory of solar system materials. Here we report the micrometeorite AAS62-34-P117 having the assemblage of corundum, hibonite, unknown Al-rich phases, FeNi metal blebs, sulfide, and phosphate embedded in Al-rich silicate composition, and Pt-group element nuggets dispersed throughout the micrometeorite. Here, we report the presence of corundum in micrometeorites as a major refractory phase with sizes greater than ~10 μm. The Al-rich phases have Al2O3 ~50–70%, such high Al phases are not known from meteoritic components either in chondrules or refractory inclusions. In addition, the Ca content is extremely poor to relate it directly to known refractory inclusions, but is very high in Al. The presence of corundum in Al-rich phases indicates the micrometeorite to be early condensate from solar nebula that later got incorporated into Si-rich materials leading to a transformation that produced the unusual Al-rich and Ca-poor phases different from the average solar composition. The observed texture and mineralogy of the micrometeorite appears to have evolved in a nebular setting that has compositional reservoirs different from those of any known components of meteorites.