114-5 Modeling of the Formation of Sharp-Edged Depressions on Titan

Session: Geomorphology and Surface Processes Across the Solar System (Poster)

Presenting Author:

Authors:

Abstract:

Sharp-edged depressions (SEDs) are flat-floored depressions bordered by steep interior scarps that occur in abundance within, and are the unifying element
of, both polar regions on Saturn’s large moon Titan. SEDs can be both filled and empty, with more filled lakes present in the north, and more empty lakes present in the south. SEDs seem to be key to understanding the evolution of the poles and Titan’s “hydrological” cycle, but observational constraints do not readily point to a single analogous terrestrial process that formed them. We have used the MARSSIM landform evolution model to test what combination of mechanisms, materials, and environmental conditions yields a model SED landscape that most closely matches the statistics of the observed landscape as determined by our mapping.

The cumulate planforms of many SEDs, which indicate that they have merged through growth, suggest that the “missing” material in them relative to the surrounding terrain is removed from below, presumably by dissolution. Lateral removal of material through subsurface drainage of methane precipitation that eventually collects in the seas seems plausible, with the consistent elevation of the methane lakes in neighboring SEDs supporting lateral connection through a basal porous/fractured layer. We have simulated the growth of SEDs from small seed depressions, with their distribution determined by random fractal variability, and with variable model parameters including the density of seeded depressions generated at the start of the simulation, and the permeability and “erodibility” (the rate of expansion of the SEDs) of the uplands. Our simulations are focused on trying to generate the observed morphological pattern whereby larger SEDs are very irregular in planform and smaller SEDs are more equidimensional. Our simulations support the conclusion that SEDs attained their present geometry through boundary extension and frequent merging of adjacent SEDs. The irregularity of the simulated SED boundaries is largely due to the spatial variability of erodibility. This suggests that the uplands eroded to form SEDs have considerable variation in erodibility as well, possibly due to intrinsic physical properties of the eroded material, variations in plateau height relative to lake level, and spatial variation in hydrological and solute properties. We will present our simulation results in the context of groundwater recharge and comparisons of Titan SEDs to mantled karst landscapes in Florida.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8243

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