The new horizons mission has returned a treasure trove of high-resolution image data for the pluto-charon system, revealing complex worlds with broad tectonic systems, diverse resurfacing…

This federal contract award is a grant provided by the National Aeronautics and Space Administration (NASA) Shared Services Center to the Universities Space Research Association (USRA), doing business as U.S.R.A. The $240,775.88 grant is for a research project to exploit the New Horizons spacecraft's high-resolution image data of the Pluto-Charon system. The research aims to constrain the tectonic and cryovolcanic history of Pluto and Charon through detailed geologic/structural mapping and finite element modeling of the icy shell lithospheres. The proposal addresses objectives of NASA's New Frontiers Data Analysis Program to enhance scientific return from New Frontiers missions. There is no set-aside designation for this contract, which was awarded on August 1, 2018 and is scheduled for completion on July 31, 2022.

The new horizons mission has returned a treasure trove of high-resolution image data for the pluto-charon system, revealing complex worlds with broad tectonic systems, diverse resurfacing mechanisms, and suggestions of cryovolcanic activity. We aim to exploit the new horizons image dataset, and products derived from IT such as topography, to constrain the tectonic and cryovolcanic history of pluto and charon at regional to global scales, through an integrated program of detailed geologic/structural mapping and quantitative analysis of ICY shell lithosphere stress and deformation states via finite element method models. We will use the sophisticated and powerful comsol multiphysics finite element code to create models of ICY shell lithospheres subject to several modes of loading. We will create global-scale models of the ICY shell lithospheres of pluto and charon to evaluate the effects of phenomena such as planetary DE- or RE-spinning, true polar wander, and thermal expansion and related effects from a growing lithosphere or freezing ocean. Such models exhibit spherical geometry, using appropriate symmetry boundary conditions to reduce model size where allowable. These models will incorporate effects that are missing from conventional analytic calculations, such as variations in shell thickness (including topographic basins), time-dependent behavior (including stress relief from brittle yielding and viscoelastic relaxation, and growing basin infill loads), and biases toward extensional stress states. Models will be evaluated on their consistency with the observed states of stress and deformation on pluto and charon as indicated by image-based mapping of tectonic features, with the goal of constraining the conditions that controlled the evolution of those bodies. These might include shell and ocean thicknesses, spin rate changes, polar wander magnitudes and rates, and basin fill and loading rates. We will also use smaller-scale models to address the formation mechanisms of particular regions and features on pluto and charon. These models may have planar geometry (for small features) or curved partial sphere geometries (for regional-scale features). For example, a radiating fracture system north of tartarus dorsa bears resemblance to radiating fracture systems on venus that are related to intrusive magmatic activity in the presence of a regional stress field. Models can constrain the values of regional stress components and pressurizations of potential cryomagma reservoirs that produce stress states consistent with the observed fracture patterns. The stress states calculated for models of the various scales stated above have implications for the transport of cryomagmas through the lithospheric shells of pluto and charon. We will use previously developed expressions for force balance on dike walls to calculate ascent-enhancing or -inhibiting effects of lithospheric stress states for cryomagmas, allowing US to identify locations or regions where eruption of cryolavas is facilitated. Such calculations, in conjunction with mapping of potential cryovolcanic features such as wright and piccard montes, may allow insights into eruptions in flood (widespread) or edifice-building (localized) modes. This proposal addresses objectives of nfdap to enhance the scientific return from new frontiers missions by broadening scientific participation in the analysis and interpretation of data returned by these missions. The proposal team blends experience and facility with new horizons data with expertise in structural modeling of large planetary volcano-tectonic systems and analyses of stress modulated magma ascent. We plan to exploit decades of experience in modeling and interpretation of tectonic and volcanic features and lithospheric dynamics of planets spanning the distance from venus to rhea, to allow US to extract new insights into the evolution of pluto and charon.