FROM CRATERS TO CONVECTING ICE SHEETS: A GLOBAL GEOLOGIC MAP OF PLUTO

Pluto displays diverse geologic terrains that have been processed through both endogenic and exogenic action. A global geologic map of Pluto at the 1:7M scale has been produced through examination of image mosaics, color imaging, composition data, and topography generated with data from the New Horizons spacecraft (White et al. 2022, LPSC). This geologic map helps us understand the global patterns and associations of various terrains across Pluto. The relative ages of the units are estimated using both crater densities and stratigraphic relationships where possible. We have defined six periods in Pluto’s geologic history that correspond to six groups of mapped units, each consisting of units that represent a major and distinct episode of geological activity on Pluto’s surface.

The heavily cratered units and the ~1000-km-diameter Sputnik Basin represent some of the oldest geological features on Pluto. The extremely young and uncratered (as far as can be seen given the image resolution) units of the giant, convecting ice sheet of Sputnik Planitia are the youngest units. This ice sheet is made up of volatile ices (nitrogen, methane, and some carbon monoxide – the exact proportions in the bulk of the ice are unknown) that are mobile even at Pluto’s low surface temperatures (average ~40 K) and behave like glaciers. Another set of very young units on Pluto are putative cryovolcanic terrains, which are discussed in a separate abstract (Singer et al., this meeting). Other relatively young or intermediate aged terrains include bladed, mantled, pitted, and etched units, which record the evolution of Pluto’s climate and volatile mobilization history across much of its age. Pluto’s surface also displays widespread extensional tectonism, ranging from a vast, NNE-SSW trending ridge trough system that crosses the entire hemisphere of Pluto seen well by New Horizons, to many intermediate and smaller scale graben and fractures.

We will present the geologic map as submitted to the USGS for review. We thank the NASA Planetary Data Archiving, Restoration, and Tools (PDART) program for funding.