Evidence of thrust faulting and widespread contraction of Ceres

Abstract

The surface of the dwarf planet Ceres is considered to be dominated by geological processes typical of small bodies or medium-sized icy bodies, such as impact cratering; there are also features of putative cryovolcanic origin as well as those related to flow of near-surface ice. Extensional features include regional linear troughs, fractures and pit chains, fractures associated with impact craters and with crater floors, and polygonal craters whose walls seem to be structurally controlled. However, no contractional features, which are related to thrust fault activity more typical of large silicate bodies, have been described. Here we report the presence of scarps, ridges and fractures associated with thrust faults, tectonically raised terrains and thrusted craters—all contractional features. These structures closely resemble thrust-fault-related lobate scarps on Mercury and Mars, albeit with lower displacement. They seem more abundant in high-latitude ancient terrains, perhaps owing to illumination effects that aid identification. The observed deformation implies that the crustal material is stronger than water ice but weaker than silicate rocks, consistent with our current knowledge of crustal composition and rheology. These features suggest that large-scale contraction, possibly related to differentiation processes, occurred in the history of Ceres.