A new prospect to analyse the spectral properties of v-type asteroids
M. Angrisani, E. Palomba, A. Longobardo, A. Raponi, F. Dirri, C. Gisellu
Icarus
Available online 23 October 2022
“Highlights
• The composition of the regolith particle size of groundbased 76 VIS-NIR normalized spectra of V-type asteroids, has been investigated and a new approach of analysis, i.e., a combination of spectroscopic analysis and Hapke radiative transfer model has been proposed. In particular, the obtained information from the a scatterplot analysis is used as constrain in the Hapke’s bidirectional reflectance model to retrieve modal composition and particle size information for each V-type asteroid. Spartacus asteroid seems to have a modal mineralogy consistent with the presence of olivine as suspected before (Moskovitz et al.,2010; Burbine et., 2001). This could be due to an origin from region of Vesta where olivine abundances were higher, or it could be due to its origin on another parent body that could have gone through the same thermal evolution as Vesta.
• The results of modal mineralogy from Hapke retrieval techniques are used to look for statistically significant differences among the spectral properties of V-type asteroids belonging to different dynamical subclasses because there is a possible chronologic link between impact events on Vesta and the V-type family. The most ancient V-type family, e.g. Low-I asteroids (they may date back to the Late Heavy Bombardment (LHB) epoch or even to the 4.48-Ga impact on Vesta) has an eucritic composition compatible with an ejection of the outermost layer of Vesta. Then, the Fugitive V-type asteroid material were ejected in an older (2 Ga) cratering event that produced the Veneneia basin (McSween et al., 2013) (with asteroids forming ∼1–2 Gy Ga ago, Nesvorny et al.,2008) and then there are the Vestoids family, whose dynamical parameters are still more similar to Vesta and is supposed to be the younger subclass of V-type family, could associate to Rheasilvia basin. The last two family seems to have a diogenitic composition compatible with that of the south of Vesta where the two huge craters are located.
• In conclusion, the developed procedure could be a starting point to develop a new automatic analysis method similar to the widespread supervised machine learning methods which represent an opportunity to research the difference between the V-type family asteroids from mineralogy features. We hope to augment the database of V-type asteroids to improve the statistical analysis and to check if there are eventually heterogeneity of each surface mineralogy comparing the different spectra of the same asteroids taken in different time with their shape model.”
“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).”
