The detection of water ice in Comet Hale-Bopp

We present spectra of Comet Hale-Bopp (C/1995 O1) covering the range 1.4-2.5 mu m that were recorded when the comet was 7 AU from the Sun, These spectra show broad absorption features at 1.5 and 2.05 mu m. While we recognize that much of the light from the comet is scattered from the coma, we show that some, but not all, of the absorption features can be matched by an intimate mixture of water ice and a low-albedo material such as carbon on the nucleus, Furthermore, the absence of the 1.65-mu m absorption feature of crystalline ice suggests that the cometary ice was probably in an amorphous state at the time of these observations, An unidentified additional component may be required to account for the downward slope at the long-wavelength end of the spectrum. (C) 1997 Academic Press.