A new high-resolution global topographic map of the active ocean world Enceladus has been produced from Cassini stereo images.
Digital elevation models (DEMs) from each stereo image sequence have been tied to a coincident global radius map derived from match points in our control network bundle adjustment solution, and referenced to the Cassini-derived triaxial figure of Thomas et al.
The global DEM has effective vertical precisions of <100 m over most areas and resolves most geologic structures, including craters, ridges and fracture systems >5 km across.
Our globally complete topography map shows a complex topographic signature associated with the large resurfacing area centered on the leading hemisphere, where shallow depressions on its western side arc across its center but the southern portion is high standing.
The north polar region, which is crossed by a set of throughgoing, geologically recent fractures as well as relaxed craters, is elevated several 100 m.
This elevation could be interpreted as a signature of a thicker polar ice shell, consistent with a lower than average heat flow and/or lower effective polar surface temperature, or alternatively, incipient or stalled development of a large area of resurfacing similar to that observed at the south pole (through thermal buoyancy of warmed ice).
The new map also provides improved definition on the 100-km-scale topographic basins we reported on in GRL in 2009 (SM09). Four deep depressions are identified between ~0 and 220° longitude (merging what were two depressions in the incomplete 2009 map into a large ‘wing-shaped’ depression near Samarkand Sulcus). The new elevation map also reveals no basins of similar scale and depth on the leading hemisphere or northern polar region. Hence there is no great circle alignment of basins as reported elsewhere, but there is a degree-2 alignment, roughly centered on the deepest basin identified in SM09. In SM09, Airy shell thickness and Pratt porosity, thermal or compositional explanations for the basins were evaluated; with nominal average shell thicknesses of 20-25 km from modern libration/gravity analyses, only shell thickness and porosity variations due to localized enhanced heat flows remain plausible. Such heat flows (at least several 10s of mW m-2) may signal warm hydrothermal plumes rising from Enceladus’ core.
