On the application of simple rift basin models to the south polar region of Enceladus

Abstract

1] The south polar terrain (SPT) of Saturn's moon Enceladus is a mysteriously active region that exhibits intriguing tectonic signatures and widespread fracturing. The central region of the nearly-circular SPT is depressed into the surface by a few hundred meters and bounded by a ring of cliffs roughly 1 km high. In this study, we investigate whether this depression and surrounding mountainous uplift is consistent with the morphology of terrestrial rift basins and the possibility that the SPT could have formed during a tectonic event analogous to those of such rift basins on Earth. Using three mechanical models of basin formation, we compare our predicted topography of the SPT with observed topography of the region. The first of three models we consider assumes crustal stretching by factor b, and predicts a basin depth of roughly 600 m, closely matching previously published estimates of the depth at the SPT. Models of extension and compression, assuming an elastic response in the ice crust, predict best-fit mountain uplift of roughly 1820 m and 1130 m, respectively. Our preferred model suggests that the icy shell in the SPT has been stretched, but the extension is (partially) balanced by compression along the edges of the basin leading to the uplift of the mountains along the boundary, thereby implying that the SPT may have a tectonic origin analogous to that of a terrestrial basin.Citation: Walker, C. C., J. N. Bassis, and M. W. Liemohn (2012), On the application of simple rift basin models to the south polar region of Enceladus,

Fault geometries on Uranus’ satellite Miranda: Implications for internal structure and heat flow

“…The south polar terrain boundary has been interpreted to be contractional in nature (Porco et al, 2006;Collins and Goodman, 2007;Grott et al, 2007;Helfenstein, 2010;Schultz et al, 2010;Patthoff and Kattenhorn, 2011). Other authors have suggested that an extensional boundary would better correlate with the global elevation dichotomy observed in the south polar region of Enceladus (Walker et al, 2012). Resurfaced terrains in the equatorial regions of Enceladus' leading and trailing hemispheres also exhibit ridges and grooves that may be extensional structures (Helfenstein, 2010).…”

Gravitational spreading, bookshelf faulting, and tectonic evolution of the South Polar Terrain of Saturn’s moon Enceladus

“…Existing work attributes TSF initiation to formation of tensile cracks as a result of (1) the presence of a rectangular or elliptical thermal anomaly of an unspecified origin below the SPT that led to surface extension (Gioia et al, 2007), (2) icy-shell flexing induced by tidal stress (Nimmo et al, 2007), (3) true-polar wander of the satellite (Matsuyama and Nimmo, 2008), (4) nonsynchronous rotation of Enceladus' ice shell above a global ocean relative to its solid rocky core (Patthoff and Kattenhorn, 2011), and (5) formation of a large rift basin (Walker et al, 2012). The subsequent kinematic evolution of the TSF after their initiation has been related to processes similar to those operated along divergent plate boundaries (Helfenstein et al, 2008) or strike-slip faulting with alternating senses of motion driven by cyclic tidal stress (Nimmo et al, 2007;Smith-Konter and Pappalardo, 2008).…”

A unified nomenclature for tectonic structures on the surface of Enceladus

“…(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Patthoff and Kattenhorn, 2011;Walker et al, 2012), or utilized relatively generic terms to refer to specific features. These approaches are insufficient for the classification of tectonic structures on Enceladus and a more systematic approach is required.…”