True Polar Wander of Enceladus From Topographic Data

TL;DR

This study presents evidence that Enceladus experienced a ~55° true polar wander, based on topographic data analysis revealing antipodal basins and a circumglobal belt, indicating reorientation of its ice shell and internal dynamics.

Contribution

It provides the first evidence of true polar wander on Enceladus using improved topographic data and identifies specific geological features supporting this reorientation.

Findings

Enceladus underwent ~55° TPW about the tidal axis.

Identification of antipodal basins and a circumglobal belt.

Topography reflects internal ice shell dynamics.

Abstract

Many obsects in the solar system are suspected to have experience reorientation of their spin axes. As their rotation rates are slow and their shapes are nearly spherical, the formation of mass anomalies, by either endogenic of exogenic processes, can change objects' moments of inertia. Therefore, the objects reorient to align their largest moment of inertia with their spin axis. Such phenomenon is called True Polar Wander (TPW). Here we report the discovery of a global series of topographic lows on Saturn's satellite Enceladus that we interpret to show that this synchronously locked moon has undergone TPW by ~55{\deg} about the tidal axis. We use improved topographic data from the spherical harmonic expansion of Cassini limb and stereogrammetric measurements to characterize regional topography over the surface of Enceladus. We identify a group of nearly antipodal basins orthogonal to a topographic basin chain tracing a non-equatorial circumglobal belt across Enceladus' surface. We argue that the belt and the antipodal regions are fossil remnants of an earlier equator and poles, respectively. We argue that these lows arise from isostasic compensation and that their pattern reflects spatial variations in internal dynamics of the ice shell. Our hypothesis is consistent with a variety of geological features visible in Cassini images.