Spectroscopic Comparison Between Near-Earth Asteroids and Ordinary Chondrites Meteorites

The population of NEA represents one of the most peculiar and heterogeneous classes of objects in the Solar System. In particular, as their dynamical lifetimes are shorter than the age of the Solar System, one of the most interesting aspects in the study of NEA is to understand their origin. To investigate the compositional properties of this population we started a spectroscopic survey in the visible region (0.5<lambda <1.0 mu m). To date we have obtained low resolution spectra of 1 Aten (3753 1986 TO), 4 Apollo (1864 Daedalus, 1786 Talos, 1989 JA, 2063 Bacchus), and 3 Amor (3352 McAuliffe, 4954 Eric, 5836 1993 MF). Most of them show spectra similar to those of the S taxonomic class, while Bacchus is the only one having a spectrum typical of C-type objects. Four of the observed asteroids show a spectrum that match quite consistently the laboratory spectra of Ordinary Chondrites. One of them (5836 1993 MF) shows also an absorption band centered around 0.6 mu m suggestive of the presence of aqueous altered materials. The OC are considered the remnants of the primitive solar nebula: they have been scarcely thermally processed during the evolutionary stages of the Solar System. Binzel et al. (1996, Science, 273, 946) already found a relationship between OC and some NEAs. If the idea that part of the NEAs could be the parent bodies of OC is confirmed, it would help to understand the origin of part of these objects: they would have been injected into near-Earth orbits from the main-belt reservoir.