TITANSLAKES · Titan's Lakes: Croll-Milankovitch, Seasonal and Hydrologic Cycles

A set of liquid hydrocarbon lakes and lake basins has been discovered in Titan's high latitudes. The lakes exhibit a dramatic hemispheric asymmetry; significant area fractions of the northern high latitudes are covered by lakes, while the same southern latitudes are largely devoid of such features. We consider the hypothesis and its consequences that in addition to known seasonal changes, the observed difference in lake distribution may be caused by an asymmetry in the seasons owing to the orbit. Due to Saturn's eccentricity, the instantaneous solar insolation received at Titan is asymmetric. The asymmetry drives a hemispheric difference in evaporation minus precipitation, and hence, in the accumulation of lakes on Titan's northern and southern surfaces. The effect is modulated by, and reverses with, dynamical variations in the orbit. In this picture, much like in Earth's climate and glacial cycles, the resulting vigorous hydrologic cycle has a period of tens of thousands of years. We seek to answer the following fundamental questions:1. To what extent do Titan's varying orbital parameters control the long-term volatile transport and surface reservoirs?2. How do Titan's lakes and seas respond to seasonal forcing?3. What is the relative role of subsurface transport of methane and ethane?4. What constraints and general properties may be derived in order to better understand Titan's overall climatologic and hydrologic evolution?