New Observations Show the Earliest Stages of Titan’s Radial Labyrinth Terrain Evolution

Abstract:

The origin and evolution of labyrinthic terrain remains one of Titan’s most intriguing unsolved mysteries. Characterized by heavily dissected surface morphology and a dome-like topographic profile, Titan’s radial labyrinths are thought to consist of organic material overlying the water ice crust. While the evolution of these features is not fully understood, the prevailing hypothesis for their formation involves the uplift of lithospheric ice and the overlying sedimentary layers through subsurface cryovolcanic activity, analogous to laccoliths on Earth, followed by fluvial erosion or dissolution of the sedimentary layers. Examples of fully formed, mature radial labyrinths are easily identified in Cassini SAR images. Until now, however, the earliest stages of labyrinth evolution (post uplift, pre-dissection) had yet to be observed. We have discovered multiple mounds in close proximity to radial labyrinths using the Cassini RADAR altimeter, and believe these features may represent the first step in labyrinth formation. In contrast to mature labyrinth terrain, these mounds appear entirely featureless in SAR images and are indistinguishable from surrounding plains, indicating that they have undergone little to no dissection at observable scales. Newly reprocessed high-resolution Cassini altimetry data has allowed us to extract detailed topographic profiles for these features, which we find are similar to radial labyrinths in both total relief and geographic extent. As radial labyrinths are thought to be cryovolcanic in origin and their size related to lithosphere thickness, the similar size and proximity of the featureless mounds suggests a genetic link between the two landforms. We hypothesize that these mounds are in fact the precursors of radial labyrinths: organic plains terrain that has been uplifted through intrusive cryovolcanism but has yet to be heavily eroded. This discovery could allow us to more fully explore the processes and timescales involved in labyrinth evolution on Titan.