We demonstrate that the tectonic configuration is diagnostic of a particular set of conditions that hold for the Sputnik basin and Pluto, including moderate elastic lithosphere thickness (40–75 km, with higher values favored if initial basin topography is compensated) and a basin that was pan‐shaped and shallow (∼3 km) at the time of nitrogen deposition initiation. We calculate models of stress and deformation related to this load, varying dimensional, mechanical, and boundary condition properties of the load and Pluto's lithosphere, in order to constrain the conditions that led to the formation of the observed tectonic and topographic signals. The nitrogen ice exerts a large mechanical load on the water ice outer shell crust (here also containing the lithosphere). The basin displays a broad, raised rim and is surrounded by numerous extensional fault systems, each with characteristic orientations with respect to the basin center. Sputnik Planitia on Pluto is a vast plain consisting of a nitrogen ice deposit filling a broad topographic depression, likely an impact basin. Better constraints on Miranda's heat fluxes require more information on its ice shell properties. These estimates decrease further when assuming NH 3-hydrates and porosity: 7-54 mW m −2 for 5% porosity, 6-46 mW m −2 for 15% porosity, and 4-32 mW m −2 for 25% porosity. Alternatively, if Miranda's lithosphere includes NH 3-hydrates, then our are estimates are even lower, 7-56 mW m −2 without porosity.
However, if Miranda instead has a porous lithosphere, our heat flux estimates are lower: 34-135 mW m −2 for 5% porosity, 29-114 mW m −2 for 15% porosity, and 20-81 mW m −2 for 25% porosity. These results are also consistent with heating from a past resonance, possibly an Ariel-Umbriel 5:3 mean motion resonance, estimated to have generated heat fluxes >100 mW m −2 on Miranda. Because the formation of the bounding flexure that we analyzed followed the formation of Argier Rupes, our results indicate that Miranda experienced high heat flux in the past-+ 100 100 400 Ma. Our results indicate an elastic thickness of 2.2-3.1 km and a heat flux of 35-140 mW m −2 in this region, assuming Miranda's lithosphere is composed of pure H 2 O ice without porosity. We modeled flexure associated with Argier Rupes, which separates Inverness from the Cratered Terrain. We estimated the heat flux near Inverness Corona, the youngest terrain on Miranda (-+ 100 100 400 Ma), to gain insight into recent endogenic resurfacing. Uranus's moon Miranda has a complex surface reflecting multiple episodes of activity. This extra heat is consistent with a Charon‐forming impact or (more likely) tidal heating during the Charon's initial history. Either case implies that Charon had a thinner ice shell, and was relatively hotter, than Pluto in the ancient past. Charon's landforms must have formed at the observed size or decreased over time to have modern amplitudes. This gives insight into how the landforms on Charon formed as well as the ability of Charon's crust to support variations in elevation. Mountains and valleys on Charon wider than this are respectively shorter and shallower than expected.
Pluto shows the expected result of a single slope decreasing in roughness at shorter widths, but Charon has a change in the slope at ∼150 km. We analyze the data to determine roughness using the mean amplitude of mountains and valleys for a range of widths. In this work we develop a topography data set for Pluto and Charon by mapping variations in the height along the worlds’ edges in images from New Horizons. Studying the topography of planetary bodies provides key insights into the geologic processes of their surfaces and interiors.