Variations in the near-infrared spectra of the Enceladus Plume

Saturn’s moon Enceladus has icy particles and water vapor spewing out of a series of fissures located on its South Polar Terrain that can provide insights into what is going on beneath the surface of this active world. We have analyzed near-infrared spectra from three long plume observations obtained in 2017 by the Cassini Visual and Infrared Mapping Spectrometer (VIMS). Imaging Science Subsystem images taken during these sequences show variations in brightness linked to changes in tidal stress, as well as longer term variations in the plume’s output [Ingersoll et al 2020 Icarus]. The VIMS data reveal that the shape of the plume’s near-infrared spectrum also changes on various timescales. These spectral variations imply that the changes in Enceladus' activity are associated with changes in the size and velocity distribution of the particles escaping Enceladus. We will discuss the implications of the observed spectral variations for Enceladus' plume activity.