THE FORMATION AND EVOLUTION OF BRIGHT SPOTS ON CERES (Invited Presentation)

The surface of Ceres is dotted with hundreds of anomalously bright carbonate-bearing regions, also termed “faculae,” with Bond albedos ranging from near the surface average of ~0.03 to >0.5. Faculae were classified and mapped globally to characterize their morphology and geological setting, assess possible mechanisms for their formation and destruction, and inform our understanding of processes affecting Ceres’ surface and near-surface. Faculae occur in four geological settings predominantly associated with impact craters: 1) craters pits, central peaks, or floor fractures (floor faculae), 2) crater rims or walls (rim/wall faculae), 3) bright ejecta blankets, and 4) the mountain Ahuna Mons. Floor faculae were found in eight large, deep, and geologically recent (<420 Ma ADM age) craters. The geometry and floor morphology of these craters is consistent with facula formation via either impact-induced heating and upwelling of volatile-rich materials, upwelling/excavation of heterogeneously distributed subsurface brines or their precipitation products, or a combination of these processes. Rim/wall faculae and bright ejecta blankets occur in and around hundreds of young craters of all sizes. The geometry of these exposures indicates that the rim/wall faculae were previously emplaced, either by impact processes or heterogeneously distributed subsurface processes, buried, and subsequently exhumed by impacts. A negative correlation between rim/wall facula albedo and crater age indicates that the faculae darken over time. No such correlation is observed for the floor faculae, possibly due to long-lived post-impact activity in the bright regions. Faculae may initially be produced or exposed by large impacts and buried by impact-induced lateral mixing. Models using the Ceres crater production function show that impact-induced lateral mixing should bury or destroy faculae over timescales of less than 1.25 Ga. Space weathering may also play a role in the gradual darkening and disappearance of faculae. Cumulatively, data point to a relatively recent formation or exposure of the faculae, indicating that Ceres’ surface remains active and that the near surface may still support brines.