Institute for Advanced Study/Princeton University Joint Astrophysics Colloquium

The NASA New Horizons spacecraft provided the first close look at Pluto, its moons, and environment during its close flyby in 2015. Pluto was shown to be a complex active planet with a variegated surface exhibiting heterogeneous geological processes. Over all, Pluto is a differentiated body with a rocky core, an extensive mantle of water-ice, and a significant atmosphere. On Pluto water-ice serves the structural role that silicate minerals serve on earth, supporting a surprisingly rugged topography of mountains, valleys, and rifts. Nitrogen, in contrast plays the role of water-ice on the earth, forming glaciers, and filling an ocean-sized basin. Internal radiogenic heat drives slow convection in the nitrogen sea and likely supports a global sub-surface water ocean. Variation in insolation over the Plutonian year interacts with the atmosphere to transport cryogenic ices over large distances. The atmosphere, itself is hazy, due to complex organic compounds formed by solar UV acting on nitrogen and methane. In contrast, Pluto’s large moon Charon lacks volatiles and signs of present activity, but does show fossil evidence of a now-frozen sub-surface ocean. The talk will explore these topics and more with extensive use of New Horizons imagery and 3D-topographic maps derived from the images (anaglyph glasses will be provided).