ABSORPTION-BANDS NEAR 3 MICROMETERS IN DIFFUSE-REFLECTANCE SPECTRA OFCARBONACEOUS CHONDRITES - COMPARISON WITH ASTEROIDS

We measured infrared diffuse reflectance spectra of several carbonaceo us chondrites in order to obtain additional information on the surface materials of their presumed parent bodies, C-type asteroids. The pres ence and intensity of absorption bands near 3 mu m in the reflectance spectra are due to the presence and abundance of hydrates and/or hydro xyl ions. The absorption features of the 3 mu m hydration bands of car bonaceous chondrites were compared with those of asteroids 1 Ceres and 2 Pallas. They are commonly classified into separate subtypes, G- and B-type. The spectral shapes of Pallas and Renazzo (CR2 chondrite) aro und the 3 mu m absorption band are an excellent match. This result may suggest that the amount of hydrous minerals in the surface material o f Pallas is smaller than that in the CM2 or CI chondrites, and the hyd rous minerals on the surface of Pallas may be similar to those found i n Renazzo. The spectral features around the 3 mu m band of Ceres are d ifferent from those of carbonaceous chondrites studied in this paper.