Charon s red-colored north polar terrain has been attributed to tholin-like material resulting from IPM LY-? Photolysis of methane accreting onto charon s winter pole following escape from pluto. This…

This federal contract award was granted by the Shared Services Center (SSC), a civilian agency, to Southwest Research Institute (SwRI), a nonprofit research and development organization. The $501,402.59 grant is for a 3-year research project to investigate the composition and origin of the red-colored north polar terrain on Charon, a moon of Pluto, based on data from the New Horizons mission. The project will combine exospheric modeling, laboratory experiments, and radiative transfer modeling to quantify the contribution of methane photolysis to Charon's surface coloration. This research is relevant to the New Frontiers Data Analysis Program's objective of enhancing the utilization of data from New Horizons. The contract is not set aside and allows for external participation in the analysis of New Horizons data, broadening scientific involvement.

Charon s red-colored north polar terrain has been attributed to tholin-like material resulting from IPM LY-? Photolysis of methane accreting onto charon s winter pole following escape from pluto. This proposition, if correct, would constitute a seminal discovery of the new horizons mission that significantly advances our understanding of the synergism between gas transfer, exosphericsurface interaction, and photolytic processes in the pluto-charon system. Fortunately, this hypothesis is highly testable via laboratory experiments and exospheric modeling since the required parameters of charon s surface temperatures, methane escape rate, and IPM LY-? Photon flux are constrained from new horizons observations and can be reproduced in the laboratory. We therefore propose a unique combination of laboratory experiments, a charon exospheric model, and radiative transfer spectral reflectance modeling, to quantitatively estimate the contribution of methane photolysis to the red color of charon s north polar terrain. The proposal goals will be accomplished by executing the four tasks over the three-year duration. Task (1) - apply our state-of-art exospheric modeling to estimate the spatial distribution of CH4 accretion and refractory formation on charon s surface. Task (2) - measure the LY-? Destruction cross-section/refractory yield/v-NIR color modification of photolyzed solid methane. Specifically, perform simultaneous deposition and irradiation, and estimate the refractory yield on charon at different deposition/irradiation. Task (3 & 4) - create a color map of charon s modeled surface and compare with mvic images to estimate the IPM LY-? Contribution to the red material s origin. Relevance: the proposal uses laboratory and modeling efforts to significantly advance the interpretation of new horizons mvic/lorri images, and the state of knowledge of charon s red north polar terrain, and thus the proposal is relevant to the new frontiers data analysis program s objective of enhancing the utilization of data obtained by the new frontiers missions . Additionally, the methane RAM flux onto charon and the IPM LY-? Flux are both critical constraints on our exospheric model and laboratory experiments. Both the CH4 RAM and LY-? Flux have been previously estimated from alice (ultraviolet spectrograph) observations. Accordingly, our proposal enhances the utilization of UVS data. Finally, this proposal provides an opportunity for scientists external to the new horizons team (PI raut, CO-i teolis) to conduct an investigation in collaboration with new horizons team members, CO-i kammer and collaborators howett and gladstone, thereby broadening scientific participation in the analysis and interpretation of new horizons data.