Spectral analysis of basaltic asteroids observed by the Gaia space mission

Abstract

There is a great deal of scientific interest in characterizing the basaltic asteroids (spectrally classified as V-types), as they are the key to understanding planetesimal formation and evolution in the early Solar System. These have long been recognized as parts of the crusts of fully differentiated planetesimals. Thus, their multiplicity, distribution, and physical characteristics are crucial for providing context for and constraining the theoretical evolution models of the Solar System. In this work, we perform spectral analysis with an extended data set of spectral measurements from the ESA Gaia mission Data Release 3, thus increasing the sample size of the analyzed V-types by more than three times as compared to the literature. Using the data provided by Gaia we identified ∼2000 possible V-type asteroids. About 350 of them successfully pass our data validation criteria. This sample includes 31 new V-type asteroids beyond 2.5 au and 6 in the Phocaea region. We confirm that the V-type asteroids in the middle and outer part of the main belt show distinct spectral properties compared to typical vestoids. In the inner main belt, we found a great diversity of spectral parameters among the V-types in all populations. Number of asteroids show band depths even greater than that of (1459) Magnya. Furthermore, some objects present 0.9 µm band-centers more than one standard deviation away from the typical value for vestoids. However since the DR3 band centers are often overestimated, those findings are to be confirmed. Overall our results indicate that the inner main belt may contain remnants of multiple differentiated planetesimals, not just (4) Vesta.

Dynamical evolution of basaltic asteroids outside the Vesta family in the inner main belt

“…The division into fugitives, low-i, and inner other is consistent with previous spectral and dynamical studies of V-types (Ieva et al 2016(Ieva et al , 2018Nesvorný et al 2008;Oszkiewicz et al 2023a). Fugitives are objects with a smaller semimajor axis than Vesta family members and comparable orbital inclination and eccentricity.…”

“…Origin in a different differentiated parent body cannot also be excluded. Intriguingly lithological differences between the vestoids and the low-i asteroids were recently reported by Mansour et al (2020) and differences in the median values of the 0.9 µm band depth by Oszkiewicz et al (2023a). Variations in mineralogy could be explained by different depths of excavation within the surface of the (4) Vesta or by the fact that the mineralogy of different bodies can be roughly the same.…”

“…A number of authors, for example Moskovitz et al (2008a), Roig et al (2008), Hammergren et al (2011, Migliorini et al (2017), and Oszkiewicz et al (2023a confirmed a number of basaltic asteroids in the middle main belt. Interestingly, asteroids (2566) Kirghizia and (25327) 1999 JB 63 show a possible drift from the 3:1 resonance at around 2.5 au.…”

“…However, these findings could not be confirmed by Ieva et al (2016Ieva et al ( , 2018. Recently, Oszkiewicz et al (2023a) showed that most V-type asteroids in the inner main belt have spectral properties that overlap with that of the Vesta family. However, few V-type asteroids were found with an unusually deep 0.9 µm band depth, which is more consistent with those of (1459) Magnya (Lazzaro et al 2000); thus, deeper mineralogical analysis is required.…”

“…The first of those objects was classified as V-type by Bus & Binzel (2002) during the course of the Small Main-belt Asteroid Spectroscopic Survey (SMASS). Asteroid (3307) Athabasca also has a Gaia DR3 spectrum showing band depth (ratio of reflectances at 0.75 µm and 0.9 µm) of 1.55a value that is more than 1σ away from typical Vesta family members (Oszkiewicz et al 2023a). However, spectral followup observations and deeper mineralogical analysis is needed.…”