EVIDENCE FOR TRUE POLAR WANDER ON ENCELADUS

The presence of the active hotspot at Enceladus' south pole raises the question of whether it formed in situ or if the satellite reoriented over time and moved the hotspot there from a different location. Here we extend a spherical harmonic reconstruction of Enceladus’ shape to order 16 by combining Cassini limb profile data with the positions of a large, globally distributed collection of surface control points. We have discovered an aligned arrangement of deep topographic lows that define a circumglobal band lying along a non-equatorial great circle across Enceladus' surface. In addition, we have found two antipodal basins located about 90 degrees from the great circle. We argue that these structures are evidence of True Polar Wander, where the great circle and the antipodal regions are remnants of old equator and poles, respectively. These structures may reflect latitudinal variations in the internal dynamics of the ice shell.