WILL IT BEND? INSIGHTS FROM FLEXURALLY SUPPORTED TOPOGRAPHY ON CERES

Nar Sulcus, located proximal to the most prominent tholus within the Yalode impact crater on Ceres’ southern hemisphere (280 ºE, 42 ºS), is the largest unambiguous surface expression of extensional tectonism on the dwarf planet. Geological mapping of the region revealed it to be composed of two mutually perpendicular sets of normal faults up to ~50 km long and ~10km wide with characteristic heaves and throws of ~1 km and ~500 m respectively.

We test the hypothesis that the topography and morphology of the Nar Sulcus normal faults are controlled primarily by a near-surface, thin ice-rich elastic layer. We do this in two steps. The first is by mapping the structures in Nar Sulcus from spacecraft images and comparing their topographic profiles to a single layer flexural-cantilever model for normal faulting similar to the one developed by [1]. The second is by using the aforementioned model derived elastic properties to constrain the rheology and heat flux at Nar Sulcus during its formation through a flexurally supported topography model similar to the one employed by [2]. This analysis, which is similar to analyses applied to the tethyan and europan ice shells by [2] and [3] respectively, estimates the elastic thickness, stress profile, and near-surface heat flux acting on the faults at Nar Sulcus during their formation.

Results from the flexural-cantilever model indicate that the elastic thickness of the uppermost mechanical layer in the Nar Sulcus region is 300-600 m, and that its tensile strength is slightly higher than that of pure water ice but much lower than that of even weakly lithified silicate material. Initial model heat fluxes for the region are ~10-100 mW/m², which are 1-2 orders of magnitude higher than what is currently expected to be the cerean average [4]. This could plausibly be due to solid-state diapirism, laccolith formation due to cryomagma accumulation sourced from either impact melt or endogenic reservoirs, and/or residual heat from the Yalode forming impact [5,6].

References: [1] Kusznir N. J. et al. (1991) Geo. Soc., Special Publication 56, 41-60. [2] Giese B. et al. (2007) GRL 34, L21203. [3] Nimmo F. and Schenk P. (2006) JSG 28, 2194-2203. [4] Travis B. J. et al. (2018) MAPS 1-25, doi: 10.1111/maps.13138. [5] Bland M. et al. (2018) LPSC XLIX. [6] Buczkowski D. L. et al. (2017) LPSC XLVIII, Abstract # 2117.