A Combination of Hydrated and Dehydrated Silicates on the S Asteroid 11 Parthenope?

V. V. Busarev (SSAI, Moscow University)

Reflectance spectra of 11 Parthenope in the range tex2html_wrap_inline20 with a spectral resolution of tex2html_wrap_inline22 have been obtained near it's oppositi- on in September 1993 in the course of a night using solar-type refe- rence star (HD11170). It has been done with a scanning spectrophotome- ter mounted on the 1.25 m telescope in Crimea. The spectra show some weak absorption features which may be ascribed to layer silicates. General shape of the spectra agrees with classification of Parthenope as S asteroid. Nevertheless, there are unusual weak absorption bands at tex2html_wrap_inline30 (up to tex2html_wrap_inline32 in depth), tex2html_wrap_inline34 (up to tex2html_wrap_inline36 ), and mo- re faint (ab. tex2html_wrap_inline38 ) ones at 0.47, 0.59, 0.63, 0.68, and tex2html_wrap_inline48 . It is interesting that the absorption features at 0.38 and tex2html_wrap_inline34 are like in parameters to those found by us on the M aste- roid 201 Penelope. Resembling absorption bands were registered also on the S asteroid 181 Eucharis (Vilas et al. 1993, Icarus 102, 225-231). The spectral features of Parthenope in the reflectance spec- tra are in a correspondence with a pattern of absorptions in spectrum of terrestrial chlorite (A. N. Platonov 1973. The nature of mineral colo- ring. - Kiev, Naukova Dumka Press, 98). The presence of absorption bands at 0.51 and tex2html_wrap_inline70 ( tex2html_wrap_inline72 ) attributed to pyroxenes (Burns et al. 1972, Proc. Lunar Sci. Conf. 3rd, 533-543) in the obtained spectra of the asteroid together with features mentioned above allows to suppose that combinations of layer silicates and unaltered igneous minerals are possible on 11 Parthe- nope and some other S and M asteroids.