Are the surface textures of Pluto's Wright Mons and its surroundings exogenic?

Abstract

Wright Mons, a large mountain about 150 km across and with 4 km of relative relief, is located at the southern end of Sputnik Planitia. It is superimposed and surrounded by 7–20 km wide hummocks separated by linear, roughly parallel troughs. The troughs are likely of tectonic origin. The hummocks, in turn, feature a surface texture of aligned km-scale ridges. The ridges have a narrowly unimodal orientation, locally ranging from N-S to NNE-SSW. Structural orientations of the troughs are multimodal, with one mode generally aligned with the ridges. Prior explanations for the topographic features have suggested a cryovolcanic origin, either by extrusive or eruptive mechanisms. Here a mixed endo-exogenic origin is advanced. Wright Mons and the hummocks are modeled as precipitation of effusions of CH4 gas from subsurface fractures derived from outgassing from a CH4 clathrate located at a depth of tens of kilometers. The outgassing is coupled with surface cold-trap deposition. The orientation of the ridges is suggested to reflect CH4 sublimation controlled by the dominant solar illumination direction, similar to mechanisms proposed to influence the orientation of Pluto's bladed terrain.