COMPOSITIONAL ANALYSES OF DYNAMICAL FAMILY ASTEROIDS WITH RARE TAXONOMIC CLASSIFICATIONS: 872 HOLDA (AND OTHERS?)

It has been shown that there is significant mineralogical variation with certain asteroid taxonomic classes. Gaffey et al. (1993, Icarus 106, 573-602) quantified the mineralogical variation within the populous S-class revealing at least seven different subclasses. Compositional variations have been suggested for the unusual M-class asteroids (Rivkin et al. 1995, Icarus 117, 90-100), and work is being done to quantify the mineralogical variations in this class as well (Hardersen et al. 2005, Icarus 175, 141-158). Spectral variations resulting from differences in mineralogy are present even within the rare E-class asteroids (Gaffey and Kelley 2004, LPSC XXXV, 1812). Based on this mounting experience, it seems reasonable to assume that spectral and mineralogical variations will be identified within each asteroid taxonomic class. It is generally accepted that taxonomically homogeneous asteroid families are real. Asteroids within the orbital element space of a family that do not match the taxonomic class majority are usually considered to be interlopers. Considering the mineralogical variation being identified above, taxonomic homogeneity does not guarantee origin within a common parent body. At the same time, taxonomic heterogeneity should not immediately rule out a common origin. We have been observing members of asteroid families that contain mixed and/or uncommon taxonomic classes. Our goal is to determine whether a compositional pattern exists within the taxonomic family majority and to test the mismatched minority is mineralogically compatible with the rest of the family. M-class asteroid 872 Holda is a member of the Eugenia family, which also contains C-, F-, and S-class asteroids. Until recently, the VNIR spectra of most M-class asteroids appeared to be featureless. Using medium-resolution SpeX data, Hardersen et al. (2005) have identified silicate absorption features in several M-class asteroids, which facilitate mineralogical interpretations of the objects. We have identified similar characteristics in a low-resolution (52-channel double CVF) spectrum of 872 Holda. Combined with previous data, this will allow us to begin testing the genetic reality of the Eugenia asteroid family.