Ammonia-water freezing as a mechanism for recent cryovolcanism on Pluto

Abstract NASA's New Horizons flyby of the Pluto-Charon system in 2015 exposed a multitude geologically active terrains on surface Pluto. Possible evidence cryovolcanism has been reported association with crustal scale extensional tectonic structures at Virgil Fossae and two large circular mountains, informally referred to as Wright Mons Piccard Mons. Our detailed geologic mapping surrounding region reveals additional mounds overlying main edifice narrow ravines emanating from summit, possibly produced by liquid flow. We model overpressure generated during freezing mixed ammonia-water inside an enclosed chamber Pluto's ice crust global subsurface ocean. consider scenarios spanning possible range ammonia abundance conclude that stresses due freezing-induced pressurization can exceed tensile strength create fractures for escape. results suggest ocean are both viable mechanisms Pluto may explain morphological variety cryovolcanic formations observed Horizons.