Early Evolution of the Main Belt Informed by the Compositional Diversity of Basaltic Asteroids
Abstract
We present near-infrared (0.78-2.45 micron) reflectance spectra for eight outer main belt (a > 2.5 AU) asteroids that have been taxonomically classified as V-types based on visible wavelength data. Three of these objects are spectrally distinct from all classifications in the Bus-DeMeo spectral catalogue, and thus could represent either spectral end members of the V-type taxonomic class or a small population of a new spectral type. The remainder of the sample are classified as V- or R-type. All of these asteroids are dynamically distinct from the Vestoid family, implying that they originated from differentiated planetesimals which have since been destroyed or ejected from the solar system. The 1- and 2-μm band centers of all objects, determined using Modified Gaussian Model fits, were compared to those of 47 Vestoids and fifteen HED meteorites of known composition. Formulas relating Band 1 and Band 2 centers to the pyroxene mineralogies of these asteroids were derived from the sample of HED meteorites and used to determine the Fs numbers of all asteroids. The Fs numbers of the five outer belt V- and R-type asteroids are, on average, between five and ten molar percent lower than those of the Vestoids, implying that these objects formed in a more reducing environment than Vesta. Given the complex evolution of oxygen fugacity in the solar nebula, these compositional results suggest that these outer belt basaltic asteroids formed either interior to Vesta and were later scattered to the outer belt or formed at a later epoch than Vesta.
- Publication:
-
AAS/Division for Planetary Sciences Meeting Abstracts #47
- Pub Date:
- November 2015
- Bibcode:
- 2015DPS....4710603L