Normal Faults on Ceres: Insights Into the Mechanical Properties and Thermal History of Nar Sulcus

We characterized two sets of extensional faults that comprise the Nar Sulcus region of Ceres by applying a cantilever model for fault related flexure and derived flexural rigidity values for Nar Sulcus between 2.0 · 1015 and 1.8 · 1016 N·m. This range of flexural rigidity makes Nar Sulcus mechanically akin to extensional structures on Ganymede, Europa, and Enceladus. We combine these observations with an inferred strength profile for the upper mechanical layer of Ceres and estimate its thickness to be 2.9–9.5 km. Surface heat fluxes at Nar Sulcus during its formation were likely ≥10 mW/m2 for estimated strain rates of 10−17–10−14 s−1, which is at least one order of magnitude larger than the current estimated global average. For geologically plausible heat fluxes between 10 and 100 mW/m2, we estimate an upper bound of ~30 vol.% mechanically silicate‐like phases in the near surface at Nar Sulcus, neglecting the effects of porosity. Plain Language Summary In March 2015, the National Aeronautics and Space Administration's Dawn spacecraft began orbiting the dwarf planet Ceres, the largest object in the main asteroid belt between Mars and Jupiter. Research has shown that a major volume fraction of the subsurface of Ceres may be composed of water ice. Knowing how water ice is distributed in the upper layer of Ceres is essential to understanding how the surface and interior have evolved over time. The Nar Sulcus region consists of two sets of extensional faults that we characterized in this study. We modeled the topography of these extensional faults in order to determine the elastic properties of the region. The properties we derived for Ceres' uppermost mechanical layer are similar to those of many of the icy moons of Jupiter and Saturn. Furthermore, they were used to help constrain three key parameters of this upper layer at Nar Sulcus: its mechanical thickness, its heat flow during the formation of the faults, and its water ice volume fraction. Key Points Modeling of cerean faulted topography suggests that its surface is elastically similar to many of the icy satellites of Jupiter and Saturn The near surface of Ceres at Nar Sulcus is likely ice‐rich and contains less than ~30 vol.% mechanically silicate‐like phases We estimate the surface heat flux at Nar Sulcus during its formation to be ≥10 mW/m2