LIQUID AND SOLIDS ON THE SURFACE OF TITAN - RESULTS OF A NEW PHOTOCHEMICAL MODEL

Recent radar, microwave and infrared observations of Titan suggest that a significant fraction of the surface may be covered by ice, in conflict with previous photochemical models which suggested a global ocean, 700 m deep, of ethane. We present here results of a new photochemical model, including updated reaction coefficients, and improved treatments of transport and condensation processes, which predict a lower ethane production (<285 m equivalent). We additionally consider the likely existence of a deep porous icy regolith on Titan's surface, which could ''hide'' the liquid hydrocarbons from observation, while permitting communication with the atmosphere to maintain the observed methane abundance against photolysis. This ''shallow, buried ocean'' model is compatible with current observational constraints on Titan's surface.