The Pluto System: Initial Results from the Exploration by New Horizons

The Pluto system was recently explored by NASA’s New Horizons spacecraft, which made closest approach on 14 July 2015. Pluto’s surface is found to be remarkably diverse in landforms, terrain ages, and albedo, color, and composition gradients. Strong evidence is found for a water-ice crust, geologically young surface units, ice convection, wind streaks, and glacial flow. Pluto’s atmosphere is found to be very extended, and contains newly discovered trace hydrocarbons, has an extensive global haze layer, and a surprisingly low surface pressure of ~10 microbars. Pluto’s wide range of surface expressions and long term activity raises fundamental questions about how small planets can have active processes billions of years after their formation. The geology of Pluto’s large moon Charon’s is also surprisingly diverse, displaying tectonics and evidence for a heterogeneous crustal composition; the north pole displays puzzling dark terrain. No evidence for a Charon atmosphere is found. Pluto’s small satellites Hydra and Nix are small, elongated objects with higher albedos than expected. Surprisingly, despite much improved diameter limits, no new satellites are found. We will present an overview of the New Horizons flyby, payload, and results. This work was supported by the NASA New Horizons project.