Influence of subsurface properties on water ice and methane clathrate stability on Mars

Gloesener, Elodie [UCL] Karatekin, Özgür [Royal Observatory of Belgium] Dehant, Véronique [UCL]

Thermodynamic conditions prevailing on Mars favour clathrate formation from near subsurface to deep down in the cryosphere (until several kilometers deep) and kinetics experiments showed that their dissociation, initiated by a change in temperature, pressure or composition of the reservoir, is a feasible mechanism for near-surface methane release on Mars. The depth and thickness of clathrate stability zone (CSZ) in the subsurface depend on many factors such as thermal state and composition of the crust, heat flow, average surface temperature, confining pressure and salinity of the water involved in clathrate formation. Water diffusion from the regolith plays a role in clathrate destabilization. Indeed, loss of shallow ice eliminates overburden pressure and initiates clathrate dissociation and the release of the trapped gas. In addition, the presence of water ice in the pores affects gas diffusion through the regolith. In this work, the water vapour transport in the martian subsurface and near-surface ice evolution (ice redistribution and porosity changes) are investigated using a 1D diffusive model and the different subsurface properties that influence water ice and methane clathrate stability such as thermal inertia or local heat flow are discussed.