CHARGE-COUPLED DEVICE SPECTRA OF ASTEROIDS .1. NEAR-EARTH AND 3-1 RESONANCE ASTEROIDS

Main-belt asteroids and cometary nuclei are both frequently suggested sources of the relatively shortlived near-Earth asteroids (NEAs). We examine the asteroidal origin hypothesis by obtaining new high-quality charge-coupled device reflectivity spectra of 19 NEAs and 23 asteroids near the 3:1 resonance, and by performing a systematic comparison of these two groups of spectra. The comparison makes allowances for phase reddening in the colors of NEAs and for the differential albedo bias as discussed by Luu and Jewitt ( 1989a). We employ nonparametric statistical tests to check for consistency between the color distributions of the two populations. The tests indicate that the difference between the two distributions is generally not significant at the 3σ level; however, this conclusion is dependent on the (unknown) size distribution of the NEAs. Our observations are thus compatible with the hypothesis that the NEAs are derived from the 3:1 resonance region, but do not imply that this is the only possible source region. As a by-product of this survey, we detect solid-state absorption features in the spectra of three NEAs. These features have no counterparts in the spectra of the main-belt asteroids.