A Global Geological Map of Pluto at 1:7M Scale

The flyby of Pluto in 2015 by NASAs New Horizons spacecraft returned high quality images that revealed a diverse range of terrains with disparate morphologies and crater spatial densities, implying a complex geological history. We have used established planetary geologic mapping techniques to produce a first draft of a global US Geological Survey Scientific Investigations Map at 1:7M scale for the >75% of Plutos surface that was imaged by New Horizons, which will represent a critical tool for resolving differing hypotheses of Plutos evolution. New Horizons only yielded high-resolution coverage of the anti-Charon hemisphere of Pluto (the "near side"). The sub-Charon hemisphere (the "far side") was imaged at much lower resolution, and so has necessarily been mapped at a much coarser scale than the near side. Six geological groups have been identified, each consisting of units that represent a major episode of geological activity on Plutos surface. Their interpreted chronological order from youngest to oldest is Sputnik (~3 Ma), Wright (<2 Ga), Tartarus (>2 Ga), Hayabusa (<4 Ga), Venera (~4 Ga), and Burney (4 Ga). The wide range of surface ages displayed by these groups appears to be primarily a consequence of how surface volatile distribution is affected by atmospheric, geographic, and topographic effects. There is a gradual transition across the far side from volatile-poor and ancient terrains west of Sputnik Planitia, to volatile-rich and young terrains to its east, illustrating the power of Sputnik Planitia, Pluto's prime repository of surface nitrogen ice that is contained within a deep impact basin, to regulate atmospheric circulation and the longitudinal distribution of volatiles. Furthermore, the greater extreme between volatile-rich and volatile-poor terrains in equatorial regions compared to those in the northern mid-latitudes, while the north polar region appears volatile-poor and ancient, reflects an additional control on volatile distribution by Pluto's distinct climate zones that stem from its high obliquity. Onto this global pattern are superimposed endogenic effects of widely differing ages, including the ancient ridge-trough tectonic system traversing virtually the entire near side, and the relatively recent terrains of the Wright group that are tentatively interpreted as cryovolcanic.