"IRS Spectroscopy of M-Class Asteroids"
We will conduct IRS 5.2--38 micron observations of the emission spectra of 27 M asteroids. Although the visible and near-IR spectra of these asteroids are nearly featureless, ten of these asteroids are now known to have hydration features at 3 micron (Rivkin et al., 2000) that are absent in the spectra of 15 others. We believe that high S/N spectroscopy of these asteroids in the mid-infrared is likely to reveal key compositional information not available in the near-infrared. In particular, it has the potential to resolve the question of whether the M-asteroid population is composed primarily of silicates, or metals, or both. This compositional information in turn is likely to lead to a better understanding of how widespread igneous differentiation was among the parent bodies of the current asteroid population.