Abstract
The water-vapor content in Enceladus' plume has been difficult to detect and map being constrained to infrequent observations such as close flybys and occultations. Mapping the plume's water-vapor variations can provide insights into the geological processes that affect the relationship between Enceladus' subsurface ocean and the south polar fissures (tiger stripes). In this thesis, I present the first analysis of detections of water vapor emission in near-infrared Enceladus plume spectra from Cassini's Visual and Infrared Mapping Spectrometer (VIMS). In Chapter 1, I provide a brief background of the Enceladus plume and discuss the motivation for this analysis. Chapter 1 will also discuss the format of the VIMS plume data and the methods we used to isolate the water-vapor signal. In Chapter 2, I confirm the existence of the water-vapor emission peak in the near-infrared (~2.60-2.75 microns) using a data set of 249 spectral cubes with relatively high signal-to-noise ratios. Chapter 2 will demonstrate that the signal in the VIMS data is consistent with a real water-vapor feature using model-based predictions and the strength of this water-vapor emission feature corresponds to a line-of-sight column density that is consistent with previous measurements. In Chapter 3, I map water vapor variations by plotting column densities over orbital phase. Chapter 3 will present an in-depth analysis of variations over orbital phase, variations over years of the Cassini mission, and variations within groups of observations. In Chapter 4, I discuss the implications of this analysis and future missions.