Introduction: Cassini SAR imaging of Titan’s surface exhibits several landforms that appear to be shaped by fluvial erosion and alluvial/sediment transport. These landscapes include: vast river networks feeding Titan’s many lakes and seas, their associated deltas, and alluvial fans. There are also places where sedimentary structures are expected, but not observed (e.g., terminus of channels entering northern seas). The coincidence of common sea-levels across several separated lacustrine landforms is suggestive of subsurface groundwater networks. Most mysterious, are Titan’s labyrinth terrain (Fig. A) which appear to have either been fluvially incised or surface-etched by dissolution and erosion, analogous to terrestrial karst morphology (e.g., Pamukkale in Anatolia).
Aims/Goals: Identifying and quantifying the relative importance of the primary array of physical processes responsible for shaping these varied landscapes — given Titan’s observed precipitation pattern — is central toward understanding how, to what degree, and with what efficiency organic materials are transported across its surface: How much organic transport occurs over Titan’s surface over Milankovitch timescales and what kind of implications will this have for surface feature evolution and viability of biotic life on Titan?
Methods and Preliminary Numerical Experiments: We have recently completed construction of a landform evolution model, based on the MARSSIM framework, which now includes added capabilities to take surface impacts of climatic variations into account. We consider the surface evolution of a synthetically generated landscape (Fig. B) subjected to a fixed amount of precipitation from model GCMs. We consider the concurrent operation of mass-wasting, fluvial erosion and sediment transport, and dissolution erosion. We take output eroded landscapes and degrade their appearance according to how it would be observed in Cassini’s SAR image data (e.g., Fig. C). Fig D shows a perspective view of a model run with mixed amount of dissolution and fluvial erosion. Sediment builds up at local topographic lows and landscape etching by dissolution erosion, while pronounced, is relatively muted (Fig. E). Fig. F is a model run with pure dissolution where the dissolved chemical species automatically goes underground once the flow reaches a topographic low. The landscape is deeply etched with high standing edifices emerging from chemical dissolution. Based solely on a qualitative evaluation, the resulting synthetic SAR image of this landscape (Fig. G) more closely resembles the labyrinth terrain shown in the figure.