Detection of Water Ice on Nereid
We report the detection of the 1.5 and 2.0 μm absorption bands of water ice in the near-infrared reflection spectrum of Neptune's distant irregular satellite Nereid. The spectrum and albedo of Nereid appear intermediate between those of the Uranian satellites Umbriel and Oberon, suggesting a surface composed of a combination of water ice frost and a dark and spectrally neutral material. In contrast, the surface of Nereid appears dissimilar to those of the outer solar system minor planets Chiron, Pholus, and 1997 CU_26. The spectrum thus provides support for the hypothesis that Nereid is a regular satellite formed in a circumplanetary environment rather than a captured object.
Additional Information© 1998 American Astronomical Society. Received 1998 August 6; accepted 1998 October 2; published 1998 October 23. These data were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the Universities of California, and the National Aeronautics and Space Administration. The observatory was made possible by the generous financial support of the W. M. Keck Foundation.
Published - 1538-4357_508_2_L175.pdf