  On day 138 of 2010, the plume of dust and gas emerging from Enceladus' South
Polar Terrain passed between the Sun and the Cassini spacecraft. This solar
occultation enabled Cassini's Ultraviolet Imaging Spectrograph (UVIS) and the
Visual and Infrared Mapping Spectrometer (VIMS) to obtain simultaneous
measurements of the plume's gas and dust components along the same lines of
sight. The UVIS measurements of the plume's gas content are described in Hansen
et al. (2011, GRL 38:11202) , while this paper describes the VIMS data and the
information they provide about the plume's particle content. Together, the VIMS
and UVIS measurements reveal that the plume material above Baghdad and Damascus
sulci has a dust-to-gas mass ratio that is roughly an order of magnitude higher
than the material above Alexandria and Cairo sulci. Similar trends in the
plume's dust-to-gas ratio are also found in data obtained when Cassini flew
through the plume in 2009, during which time the Ion and Neutral Mass
Spectrometer (INMS), Radio and Plasma Wave Science instrument (RPWS) and Cosmic
Dust Analyzer (CDA) instruments made in-situ measurements of the plume's gas
and dust densities (Dong et al. 2015 JGR 120:915-937). These and other
previously-published systematic differences in the material erupting from
different fissures likely reflect variations in subsurface conditions across
Encealdus' South Polar Terrain.
