Color Variation Within Inner-belt Asteroid Families

Document Type

Conference Proceeding

Publication Date


Publication Title

American Astronomical Society, Department of Planetary Sciences


We studied the Sloan Digital Sky Survey (SDSS) colors of four inner-belt families: Flora, Baptistina, Erigone, and Nysa. Each of these asteroid families divides cleanly into two clusters in color space: one belonging to a primitive asteroid taxonomic class while the other to a non-primitive class. The clusters were determined using two techniques: Principal Component Analysis and AutoClass. We also found that the Wide-field Infrared Survey Explorer (WISE) albedos for each of the clusters were clearly different, which is nicely consistent with our SDSS clusters. These results indicate that there are at least two populations within each of the four families. This dichotomy within each family has two possible explanations. One possibility is that the two clusters represent contamination resulting from a purely dynamical definition of the family. This contamination can come from adjacent, yet distinct asteroid families or a non-family background population. Or a plausible, but less favored explanation, is that the color and albedo clusters within each family could represent surprisingly different compositional units within the parent body. Based upon a Yarkovsky analysis, significant contamination between families is the favored explanation for our results. These results may allow us to refine current methods of family definition and help minimize interlopers.