¹M.Angrisani,¹E.Palomba,¹A.Longobardo,¹A.Raponi,¹F.DirriC.Gisellu
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115320]
¹INAF-IAPS Rome, Via Fosso del Cavaliere,100 Rome, Italy
Copyright Elsevier

Among main belt asteroids, some have a spectrum similar to Vesta so they are taxonomically classified as V-type asteroids. Probably they were removed from Vesta and migrated to their current positions via some still unknown dynamical mechanisms. Several issues on the relationship between V-type asteroids, Howardite -Eucrite -Diogenite (HED) meteorites and Vesta are still unresolved. Although some of them can be directly linked to (4) Vesta, forming its dynamical family, others do not appear to have a clear dynamical link, thus suggesting the existence of other basaltic parent bodies. In this work we present a new approach of analysis to investigate 76 VNIR V-type asteroids spectra downloaded from PDS. The composition of the regolith and particle size of V-type asteroid have been investigated with a combination of spectroscopic analysis and Hapke radiative transfer model. Retrieved particle sizes are very small, with a mean value of 20 μm.

Therefore, we look for statistically significant differences among the modal mineralogy of V-type asteroids belonging to different dynamical subclasses. It seems there is a possible chronologic link between impact events on Vesta and the V-type families. The most ancient V-type family, e.g. Low -I asteroids, seems to have a eucritic composition compatible with an ejection of the outermost layer of Vesta. The Fugitive V-type were probably ejected in an older cratering event that produced the Veneneia basin while the Vestoids family, whose dynamical parameters are still more similar to Vesta and which seems to be the youngest family among them, could be associated to Rheasilvia basin. The last two families seem to have a diogenitic composition compatible with that of the south of Vesta, where the two huge craters are located.

Spartacus asteroid is also analysed and it was found to have a modal mineralogy consistent with the presence of olivine as noted before (Moskovitz et al.,2010; Burbine et al., 2001).

¹C.J.Renggli,^2,3J.L.Hellmann,^2,4C.Burkhardt,¹S.Klemme,¹J.Berndt,¹P.Pangritz,^2,4T.Kleine
Geochimica et Cosmochimica acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.10.032]
¹Institut für Mineralogie, University of Münster, Münster, 48149, Deutschland
²Institut für Planetologie, University of Münster, Wilhelm-Klemm Straße 10, 48149 Münster, Deutschland
³Department of Geology, University of Maryland, 8000 Regents Drive, College Park, Maryland 20742, USA
⁴Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
Copyright Elsevier

As a moderately volatile, redox-sensitive chalcophile and siderophile element, Te and its isotopic composition can inform on a multitude of geochemical and cosmochemical processes. However, the interpretation of Te data from natural settings is often hindered by an insufficient understanding of the behavior of Te in high-temperature conditions. Here, we present the results of Te evaporation and isotopic fractionation in silicate melting experiments. The starting material was boron-bearing anorthite-diopside glass with 1 wt.% TeO2. The experiments were conducted over the temperature range of 868-1459 °C for 15 minutes each, and at oxygen fugacities (logfO2) relative to the fayalite-magnetite-quartz buffer (FMQ) of FMQ−6 to FMQ+1.5, and in air. Evaporation of Te decreases with decreasing fO2. For high-temperature experiments performed at >1200 °C Te loss is accompanied by Te isotope fractionation towards heavier compositions in the residual glasses. By contrast, Te loss in experiments performed at temperatures <1200 °C typically resulted in lighter Te isotopic compositions in the residues relative to the starting material. In air, Te evaporates as TeO2, whereas at lower oxygen fugacities we predict the evaporation of Te2, using Gibbs free energy minimization calculations. In air, the experimentally determined kinetic isotopic fractionation factor for δ128/126Te at T > 1200 °C is αK = 0.99993. At reducing conditions, Te likely substitutes as Te2- for O2- in the melt structure and becomes increasingly soluble at highly reducing conditions. Consequently, Te evaporation is not predicted for volcanic processes on reduced planetary bodies such as the Moon or Mercury.