GEOLOGICAL MAPPING OF DWARF PLANET CERES FROM NASA’S DAWN MISSION

A geologic mapping campaign was conducted during NASA’s Dawn Mission at dwarf planet Ceres, including production of a global geologic map and a series of 15 quadrangle maps to determine the variety of process-related geologic materials and the geologic history of Ceres. Mapping results demonstrate that all major planetary geologic processes (impact cratering, volcanism, tectonism, and gradation (weathering-erosion-deposition)) have occurred on Ceres. Ceres crust, dominated by altered and NH₃-bearing silicates, carbonates, salts and <30% water ice, preserves impact craters at all sizes and degradation states, and is interpreted to represent the remains of the bottom of an ancient ocean. Volcanism is manifested by cryovolcanic domes, such as Ahuna Mons and Cerealia Facula, and by explosive cryovolcanic plume deposits such as the Vinalia Faculae. It is possible that the volcanism of the faculae is impact-induced, as it occurs within the 92-km diameter Occator impact crater. Tectonism is represented by several catenae extending from Ceres impact basins Urvara and Yalode, terracing in many larger craters, and many localized fractures around smaller craters. Gradation is manifested in a variety of flow-like features caused by mass wasting (landslides), ground ice flows, as well as impact ejecta lobes and melts. Our working chronostratigraphy and geologic timescale for Ceres is centered around major impact events. Ceres geologic periods include Pre-Kerwanan, Kerwanan, Yalodean/Urvaran, and Azaccan (the time of rayed craters, similar to the lunar Copernican). The presence of geologically young cryovolcanic deposits on Ceres surface suggests that there could be warm melt pockets within Ceres shallow crust and the dwarf planet remain geologically active.