Abstract Multiple lines of evidence suggest that a methane‐clathrate crustal layer exists in Titan. However, we have not directly confirmed the existence or thickness of this hypothesized layer, a potentially important methane reservoir. Here, we model impact crater formation and subsequent viscoelastic evolution in Titan's ice shell with methane‐clathrate crusts 0–15 km thick. We show that Titan's peculiarly shallow impact craters are most consistent with the presence of a methane‐clathrate crust, which influences the initial crater shape and rate of topographic relaxation over time. Craters that form in a pure‐water‐ice shell are kilometers deeper than those observed on Titan, even after relaxation. The methane‐clathrate crust thickness influences the thermal and yield strength profiles, which affect the initial crater shape and topographic evolution. Impacts into methane‐clathrate crusts form shallower craters and they topographically relax to depths closer to what is currently observed. We find that the simulations of impacts into a 5 km thick clathrate crust best reproduce the observed crater topography. Such a crust would store at least ∼250× the current mass of atmospheric methane for potential replenishment. The clathrate crust drastically insulates Titan's interior, and implies that Titan is more active than previously assumed.
Schurmeier et al. (Fri,) studied this question.