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C. de Bergh (Obs. Paris, France), B. Schmitt (Lab. Planetologie Grenoble, France), R.P. Binzel (M.I.T., USA), S.J. Bus (Univ. Hawaii, USA)
Phoebe, irregular satellite of Saturn, is a peculiar object with its dark, neutral surface resembling that of a C-type asteroid and the presence of water ice on its surface (with probably a very non-uniform distribution, given the important albedo variations observed by Voyager). It is most probably a captured object, but its origin is uncertain.
Two visible spectra covering the range 0.4-0.9 micron and corresponding to opposite sides of the satellite have been recently obtained by Buratti et al. (Icarus, 155, 375, 2002). They are completely flat. Concerning water ice, it was detected a few years ago by Owen et al. (Icarus, 139, 379, 1999) at UKIRT and Brown (Astron. J., 119, 977, 2000) at the Keck telescope.
To achieve more complete spectral coverage and better define the water ice absorptions, we recorded a spectrum of Phoebe with the SpeX instrument on the IRTF telescope on January 12, 2002. The observations were made while the object was at an air-mass of 1.08. This spectrum covers the 0.8-2.5 micron range at an average spectral resolving power of about 100. The spectrum is flat between 0.8 and 1.3 micron. The 1.5 and 2 micron absorptions of water ice are well defined. The spectra have been modelled with different mixtures of water ice and dark contaminants.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.