Labyrinth terrain on Titan

Summary

The Cassini/Huygens mission revealed a terrain type on Saturn's moon Titan of dissected, elevated plateaux with a high density of valleys named labyrinth terrain. We define four subtypes of labyrinth terrains: valleyed, polygonal, finely-dissected, and the possible outlier Kronin Labyrinth. We mapped the locations of all labyrinths imaged by Cassini and found they are distributed preferentially at high latitudes. We characterize the labyrinths by morphometric parameters such as intervalley width, valley width, and percent valleys. We find many labyrinths contain closed valleys, which constrains their formation and evolution. We also examine their low microwave emissivity spectral characteristics and find that the labyrinths are consistent with a bulk composition of dominantly organic materials, with some component of water ice – characteristics similar to Titan's undifferentiated plains. Our analyses show that labyrinths are ancient terrains – only the mountains and hummocky terrains are older. This implies that significant organic production occurred early in Titan's history. The organic inventory represented by the labyrinths is estimated to be 15–42% of the solid organic inventory of Titan (or 14–35% of the total surface organics, if the hydrocarbons of the lakes and seas are also included). Our preferred formation of the labyrinth terrains is erosion through dissolution and fluvial processes that dissect the plateau in a manner similar to dissolution geology (karst) on Earth. This scenario requires that the organics that make up the labyrinth terrain be soluble in methane and/or ethane liquids. It also suggests that the origin of the plateaux may have derived from Titan's past chemical production and subsequent depositional record.