The Insulating Effect of Methane Clathrate Crust on Titan's Thermal Evolution

Saturn's largest moon Titan is unique for its dense, methane-rich atmosphere, with ongoing complex organics chemistry, and the hydrocarbon lakes and seas on its frigid surface. Titan also harbors a subsurface water ocean, and its ice shell is likely capped by a thick crust of low-conductivity methane clathrates that are very stable under Titan's surface conditions. Here, we investigate the effect of this insulating clathrate crust on convection in the ice shell. Without the clathrate crust, convection occurs below a stagnant lid that is a few tens of kilometers thick and limits the exchange between the surface and the deep ocean. We show that a 5-10 km thick clathrate crust reduces the stagnant lid thickness about threefold thus increasing the potential for the ocean-surface exchange. Moreover, the insulating effect of clathrates dramatically decreases the amount of extracted heat thus limiting the freezing rate of Titan's ocean.