Surface composition of Pluto's Kiladze area and relationship to cryovolcanism

Abstract

A link between exposures of water (H2O) ice with traces of an ammoniated compound (e.g., a salt) and the probable effusion of a water-rich cryolava onto the surface of Pluto has been established in previous investigations. Here we present the results from the application of a machine learning technique and a radiative transfer model to a water-ice-rich exposure in a geographic feature on Pluto named Kiladze and its surroundings. We demonstrate the presence of an ammoniated material suggestive of an undetermined but relatively recent emplacement event. Kiladze lies in a region of Pluto's surface that is structurally distinct from that of the areas where similar evidence points to cryovolcanic activity at some undetermined time in the planet's history. Although the Kiladze depression superficially resembles an impact crater, a close inspection of higher-resolution images indicates that the feature lacks the typical morphology of a crater. Here we suggest that a cryolava consisting of water carrying an ammoniated component may have emerged onto the surface at the Kiladze area via one or more collapses, as in a resurgent volcanic caldera complex. Large regions east of Kiladze also exhibit the presence of H2O ice and have graben-like structures suggestive of cryovolcanic activity, but the existing data are not amenable to the detailed search that might reveal an ammoniated component.