A Mechanism for Replenishment of Methane in Titan’s Atmosphere by Intrusive Methane Clathrate Hydrate Thermal Destabilisation

Titan’s atmospheric methane requires replenishment due to photolysis-driven loss. We have modelled the destabilisation of an upper layer of methane clathrate hydrates (MCH) containing some ammonia (NH3) through thermal interaction with a warm ice intrusion (such as a diapir). Given the potential abundance of MCH in Titan’s crust, the volumes of methane released by such episodic thermal exchange processes are sufficient to maintain Titan’s current atmospheric methane abundance over geological time. The presence of ammonia is required for MCH destabilisation. The destabilisation process relies on the concentration of ammonia in partial melts that form in pockets in the Titan crust. We find that the minimum ammonia content in these pockets of partial melt required for MCH to be a source of methane supply (caused by thermal destabilisation by warm (260 K) ice intrusive bodies) is 26 wt% if the MCH layer is 5 km thick and 21 wt% where the MCH layer is 10 km thick. The volumes of water-ammonia remaining after MCH destabilisation and methane escape can possibly provide sources of postulated cryovolcanic liquids on Titan’s surface.