Fluid-driven surface change in sediment-limited interdune environments and relevance to Titan

• Titan’s interdunes display considerable SAR variability also observed on Earth. • Seasonal fluid flow surface changes drive Earth’s interdune SAR variability. • Comparable processes may be occurring on Titan. Interdune areas and purported playa-type environments in Saturn’s moon Titan’s dune fields show substantial spatial variability in radar backscatter expression. Using examples from Death Valley, the Middle East, and northern China, this work evaluates terrestrial causes of spatial backscatter heterogeneity in similar aeolian environments. It introduces the importance of temporal change detection in interdune area backscatter expression. Using optical images, time-series radar synthetic aperture radar images, and coordinated meteorological and river discharge data (where available), backscatter variations are related to spatially changing sedimentary environments within sediment-limited areas, i.e., interdune and playas, and temporally changing surface or near-surface moisture conditions. In terrestrial environments, backscatter expression varies over seasonal and annual timescales as a function of the cumulative history of surface change, primarily driven by changes in surface and near-surface moisture from either precipitation or groundwater table rise and fall. On Titan, evidence for equatorial methane flow channels suggests that arid-climate surfaces may undergo temporal evolutions like those observed on Earth. Fluid flow and evaporite formation play crucial roles in the existence and alteration of patterns in Earth’s interdunes. By analogy, these mechanisms are also expected to be at work on Titan. Despite differences between terrestrial and Titan radar observations, considering surface dynamics and evolution over time on Titan may be critical for analyzing its arid, equatorial environments.