Elevation distribution of Titan's craters suggests extensive wetlands

Using a new global topographic map of Titan, we find that craters on Titan preferentially lie at higher than average elevations. We explore several explanations for this observed behavior, and judge the most reasonable explanation to be the presence of widespread wetlands of liquid hydrocarbons at low elevations over much of geologic time. Impacts into a shallow marine environment or a saturated layer of sediments more than several hundred meters thick would produce crater morphologies similar to terrestrial submarine impacts. These are known to lack significant topographic expression, and would thus be difficult to observe with the Cassini spacecraft. Since Titan's near-surface methane inventory likely fluctuated over geologic time, with episodic delivery and continuous depletion, a few craters at low elevations can nonetheless be expected. (C) 2013 Elsevier Inc. All rights reserved.