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 cratering1,2; there are also features of putative cryovolcanic origin3 as well as those related to flow of near-surface ice4. Extensional features4–6 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 bodies7–11, 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 Mercury7,8 and Mars9,10, 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 composition12 and rheology13. These features suggest that large-scale contraction, possibly related to differentiation processes, occurred in the history of Ceres. Contractional features such as scarps, ridges and fractures from thrust faults are typical of large silicate bodies such as Mercury and Mars. Evidence for similar features on Ceres suggests the possibility of large-scale contraction on this icy body.