Paper No. 9
Presentation Time: 11:00 AM
EXOTIC EUROPA: GLOBAL GEOLOGIC MAP AS A REFERENCE FOR FUTURE STUDY
Europa’s young surface age, extensive resurfacing, and indications of a sub-surface ocean elevate its astrobiological potential and make it a compelling focus for planetary geological study. Knowledge of the global distribution and timing of geologic units is key to understanding the satellite’s history and for identifying features relevant for future study. We have produced an updated and enhanced 1:15M scale global geologic map of Europa based on a combined Galileo
photomosaic. Mapping techniques used for Europa differ from other planetary maps. Wide variations in resolution and viewing geometries prevent mapping subtle variations in unit textures and demand attention to unit appearance across resolution and phase boundaries. This map presents a proportionate representation of globally consistent units and features. Four material unit types are recognized: plains, linea, chaos, and crater materials. Plains material includes ridged, lenticulated, and banded units. Linea material, mapped as structures, includes bands, ridges, ridge complexes, flexūs, and undifferentiated lineaments. Chaos material is subdivided into lenticulae, microchaos, fractured, general (“platy”), blocky (“knobby”), subdued, and undifferentiated chaos. Crater materials include secondary materials, ejecta, and morphology associated materials. Unit definitions are aimed at understanding formation processes in relation to the exotic composition of Europa’s crust and the possibility of a past or present global ocean beneath the surface ice layer.
The paucity of impact craters prevents relative age determinations based on crater density frequencies. We establish stratigraphic markers as a function of framework lineament cross-cutting relationships and illustrate the surface history through four periods: 1) formation of ridged plains, 2) disruption of plains by lenticulae, bands, and lineaments, 3) formation and disruption of chaos, and 4) continued chaos formation, emplacement of young impact craters, and building of prominent double ridges. This global geologic map provides a synthesis of this unique satellite’s overall history and will be a useful frame of reference for future landing site studies, orbital and flyby studies of Europa’s geology and astrobiology, and jovian system exploration.