| Summary: | A structural analysis of the South Polar Terrain (SPT) and surrounding southern regions of Enceladus was carried out through the mapping of nearly 1000 fractures, folds, and ridges to determine the strain field recorded in these structures and the possibility of subsurface water on the satellite. Mapping performed from NASA’s Cassini images and structure orientations plotted on rose diagrams reveal a primary set of fractures trending ~30° W- 60° W and an orthogonally trending set of fractures striking ~300° W- 330° W. These fracture patterns are incompatible with current models that indicate shifting strain fields, but rather show a long history of consistent, daily tidal stresses acting on the moon because of its elliptical orbit of Saturn. Based on kinematic analysis of fractures on Enceladus and their cross-cutting relationships and secondary structures such as folding and ridges, fractures in the South Polar Terrain (SPT) are not solely extensional, contractional, or strike-slip, but a combination of these strain mechanisms actually exists. A set of four en echelon fractures termed “tiger stripes” and the accompanying Set 1, 2, and 3 fractures are oblique extensional and/or oblique contractional fractures and are interpreted to be formed from tidal forces from Saturn acting on the satellite. To explain plumes that erupt water vapor and ice from the SPT, subsurface water has been included in various Enceladean models. Funnel-shaped structures present in the peripheral areas of the SPT with arcuate folds towards the direction of flow as well as thin parallel fractures lining the apexes of the folds may indicate the presence of water below the surface. Antarctic ice stream models, said to overlie vast subsurface lakes, closely mimic these observed structures on the satellite both quantitatively and geometrically.
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