Comparing Enceladus to Comets: Implications for Enceladus' Activity

Despite obvious physical differences in size, shape, and surface albedo between Enceladus and cometary nuclei, the compositional similarities between the vented gases from Enceladus and the gases in cometary comae are striking. The approximately 1028 molecules/s of material emitted from Enceladus, composed mostly of water with some hypervolatile species, flows out in jets similar to those seen for moderately active comets. Using recent data from Cassini instruments, including the Ion and Neutral Mass Spectrometer (INMS), the Visual and Infrared Mapping Spectrometer (VIMS) and the Imaging Science Subsystem (ISS), we investigate the compositional similarities between Enceladus' plumes and cometary comae and we compare the physical properties (densities, speeds, collimation) of the plumes and cometary jets. We will discuss the implications our findings have for various aspects of the origin and evolution of Enceladus.