Testing the cryovolcanism and plate bending hypotheses for Charon's smooth plains

Abstract

Topographic moats are found at the edges of Charon's Vulcan Planitia, both where the plains meet the higher elevation terrain in Oz Terra, and surrounding isolated mountains within the smooth plains. The curved edges of the moats have been hypothesized to represent either the front of a cryolava flow from the emplacement of the plains material, or the result of elastic flexure of the plains surface due to the load of adjacent mountains or sinking crustal blocks. We tested both of these hypotheses by taking topographic profiles across the moats and comparing the observations to theoretical predictions from two lava flow models and two plate bending models. The algorithm we used returns a correlation coefficient as well as the parameter values for the theoretical model necessary to match the topography. Our results show that the plate bending models provided the best fits for the topography, though the lava flow models provided good matches for a few profiles. Our results for elastic thickness of ~1 km for a continuous plate or ~3 km for a broken plate are similar to results previously derived at Serenity Chasma. The values obtained for Bingham yield strength of ~10 kPa are also consistent with previous results from hypothesized cryovolcanic material on Ariel and Charon.