Near-Infrared Spectroscopy of Volatiles on Icy Saturnian Satellites

Anne Verbiscer

Using TripleSpec, a new spectrograph at the Apache Point Observatory, we have recently acquired new high-resolution (R~3000) near-infrared spectra 0.9 - 2.5 microns of Iapetus centered at longitudes 160 W and 359 W, Tethys' leading hemisphere, and the trailing hemispheres of Enceladus and Rhea. Several of these spectra show the absorption feature of ammonia hydrate at 2.21 microns also seen in the spectrum of Tethys' trailing hemisphere. While this feature was also suggested in a spectrum of Enceladus obtained in 2004 at a latitude of 24 S, it does not appear in the new spectrum centered at latitude 11 S obtained in 2008 at the same longitude. In 2004, more of Enceladus' south polar terrain was visible than in 2008, and images returned from the Cassini Spacecraft Imaging Science Subsystem (ISS) have since shown that this region on Enceladus is particularly blue in addition to being geologically active. I will compare these with observations of volatiles on other icy bodies in the outer Solar System.