Formation of Fluvial Gravel Pavements as an Explanation for Persistence of Ancient Cratered Terrain on Titan

English Abstract:

Portions of the equatorial region of Titan are fluvially eroded into banded (crenulated) terrain, some of which contains numerous circular structures that are likely highly degraded large impact craters. Such cratered terrain probably survives from the late heavy bombardment. A number of explanations for the survival of such terrain to the present epoch include very inefficient fluvial erosion, late acquisition of a dense atmosphere, and intermittent presence of sufficient methane in the atmosphere to support precipitation and runoff. No mechanism has been unambiguously demonstrated to operate on its surface that can chemically of physically break down ice that is likely the most important component of Titan’s crust. We quantitatively model a scenario in which fluvial erosion on Titan has largely involved erosion into an impact-generated megaregolith that contains a modest component of gravel-sized debris. As the megaregolith is eroded, coarse gravel gradually accumulates as a lag pavement on channel beds, limiting further erosion and creating a dissected, but largely inactive, or senescent, landscape.