THE EUROPA GLOBAL GEOLOGIC MAP

Evaluating the potential habitability of the icy ocean worlds of the outer planets requires an understanding of three main components: the chemistry and composition of the material making up the body, the sources of chemical disequilibrium available for potential metabolic processes, and the geology that drives the interaction between the surface and the deeper interior of the body. Here, we focus on the latter component for Europa, creating a global geologic map at the scale of 1:15M. The geologic units can be divide into four categories: (1) crater materials and its subunits: continuous crater ejecta, Pwyll radial crater ejecta, and Pwyll crater ray material—including the primary impact crater and its local deposits and farther ranging ejecta material; (2) Various morphological types of chaos materials identified as: high relative brightness, mottled, low relative brightness, and Moytura chaos material— disrupted terrain consisting of blocks of existing terrain that have been broken up on a scale of 100s of meters to kilometers within a matrix material; (3) band material—linear to curvilinear zones with a distinct, abrupt albedo change from the surrounding region; and (4) regional plains material—distributed across all latitudes and characterized by subparallel to cross-cutting ridges and troughs. In addition to the geologic units, a number of linear features are identified including: depression margins, troughs, multi-ring structures, cycloids (flexus), high relative brightness band linea, band linea, ridges, and undifferentiated linea. We also have a few point features (at the global scale), including craters, central peak structures, and microchaos—denotes small (5-20 km) patches of discontinuous chaos material. The completed map constrains the distribution of different Europa terrains and provides a general stratigraphic framework to assess the geologic history of Europa from the regional to the global scale. This map was accepted for publication by the USGS in May 2020 and is currently in the final stages of production.