Investigating the Evolution of Surface Features on Saturn’s Moon Titan
Schurmeier, Lauren Rachelle
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Saturn’s icy moon Titan is thought to be the most Earth-like world in our solar system. There is overwhelming evidence of exogenic processes (aeolian, lacustrine, fluvial, and impact cratering), but it is unclear if exogenic processes (volcanism, viscous relaxation, diapirism, and tectonics) are important in shaping Titan, like they are on Earth. I study the evolution of three types of surface features to understand better the relative importance of endogenic and exogenic processes in shaping the Titan that we see today. First, I investigate why Titan’s existing impact craters are anomalously shallow using finite element modeling. Second, I investigate how several large mountainous plateaus are supported and formed on Titan, again using finite element modeling. Third, I investigate how the medium-size, organic-rich dome shaped topography (Labyrinth terrains) formed. I use scaling relationships based on diapirs and intrusive volcanic laccoliths on other planetary bodies to choose the most plausible formation mechanism. I find that Titan’s craters cannot undergo topographic relaxation under normal conditions, but will relax when filled with large amounts of low thermal conductivity sand from nearby sand seas. In addition, the large mountain plateaus cannot be supported by Airy isostasy (the primary way that mountains supported on Earth) nor formed through crustal thickening (tectonics). Instead, they must be supported by the lithosphere, or Pratt Isostasy, both of which could form through cryovolcanic (volcanism of ice and water) processes. Furthermore, I identify putative morphological evidence for extrusive cryovolcanism at one plateau location. Finally, the scale and spacing of the dome-shaped Labyrinth terrains is not consistent with diapirism, but is consistent with an intrusive cryovolcanic laccolith forming at the base of Titan’s lithosphere within its water ice shell. Overall, I find that these three types of surface features indicate that both exogenic and endogenic processes are important contributors to shaping the Titan that we see today, and that endogenic processes such as topographic relaxation and cryovolcanism may be more prevalent on Titan than previously thought.