Fretted channels in Arabia Terra on Mars: Regional stratigraphy and implications for their formation

Fretted terrain and fretted channels in northeastern Arabia Terra are among the morphologically most diverse and least understood landscapes on Mars, and the timing and nature of their formation remain enigmatic. Understanding their formation is key to reconstructing the evolution of the dichotomy boundary and constraining past hydrologic and climatic conditions on Mars. Therefore, we reassess the regional setting of fretted channels and terrain, define initial and subsequent stratigraphic components, and deconvolve their younger glacial overprint. Comparing Arabia Terra's western and eastern regions reveals that, although they have similar initial stratigraphy, their subsequent evolution diverged markedly. This led to the formation of outflow channels in the west and fretted channels in the east. Our synthesis of regional and stratigraphic relationships provides new context and constraints on the nature and origin of fretted channels, which are exclusively located in eastern Arabia Terra. We identify evidence consistent with a subsurface origin of fretted channels, including closed depressions, plateau surface collapse, and beaded pits merging into fretted channels. Based on our systematic analysis of fretted channel elements and the regional stratigraphy of the Arabia Terra upland plateau, we suggest that fretted channels are intimately related to the emplacement of regional volcanic plains and snow/ice accumulation, and we outline questions and approaches to further test this hypothesis.