Detailed Mineralogical Characterizations of Four S-Asteroids: 138 Tolosa, 306 Unitas, 346 Hermentaria, and 480 Hansa

The S-asteroid taxonomic class is the second largest grouping of main-belt asteroids that are primarily located in the inner main belt (a < 3.0 AU) [1]. These asteroids have historically been the subject of interest within the asteroid community for several reasons. Continuing discussions about the nature of the S-asteroids (ordinary chondrite-like or thermally-evolved) and the putative space weathering effect on S-asteroids serve as examples of issues currently unresolved within the community [2,3]. Despite this general interest, detailed mineralogical investigations of individual S-asteroids has been relatively rare. A few workers have studied individual, or small groups of, S-asteroids [4,5,6,7]. Gaffey et al. [2] published their S-asteroid survey in 1993 that characterized 39 of the 144 then-classified S-asteroids. Despite the work already accomplished, the need exists to rigorously characterize the remaining S-asteroid population to gain a better understanding of these asteroids origin, nature, and physical characteristics.