THE MARIA DYNAMICAL ASSOCIATION AND 433 EROS: THE FIRST MINERALOGICAL TEST

The 81-member Maria dynamical asteroid group is located adjacent to the outer boundary of the 3:1 mean motion resonance with Jupiter near 2.5 AU. This group could be an important contributor to the terrestrial meteorite flux and may be a source of ordinary chondrites.

Based on dynamical arguments, this group was identified previously as the most promising potential source of large near-Earth asteroids, including 433 Eros. Visible-region spectra for several Maria group asteroids compare favorably with spectra in the same wavelength region for Eros. While the visible spectra are grossly similar and suggest a potential connection between Eros and some members of the Maria group, they fall short of demonstrating a quantified compositional link. A mineralogical investigation of this family will shed light on the important issues of the source of ordinary chondrites and the rate of orbital diffusion adjacent to a major resonance.

As part of the Family Asteroid Compositional Evaluation Survey (FACES), we obtained near-IR spectra of 433 Eros on June 29, 2000 at the NASA Infrared Telescope Facility. Analyses of the spectra allowed us to derive the mineralogy (olivine-to-pyroxene abundance ratio and pyroxene chemistry) for Eros. On the same night in June 2000 we also collected near-infrared spectra for three members of the Maria dynamical group, including 652 Jubilatrix, 714 Ulula, and 1215 Boyer. Ulula is an S-class asteroid, but Jubilatrix and Boyer have not been classified taxonomically. The spectra of the three Maria group asteroids exhibit silicate absorption features typical of olivine-pyroxene mixtures. Analyses of the new near-IR spectra for these asteroids should provide detailed mineral abundances and chemistries. These data will allow us to apply the first rigorous geologic test to the Maria dynamical association and to test the proposed genetic connection to 433 Eros. Early results for Jubilatrix show it to be within or near the S(VII) subclass of asteroids. Meteorite analogs for this asteroid may include basaltic achondrites or mesosiderites. At least two possibilities exist at this stage: (1) Eros and Jubilatrix are not genetically related, or (2) Jubilatrix represents the basaltic component of the Eros parent body. The latter case would infer that Eros is a mantle fragment of a differentiated parent body.