LAUSR

Abstract The Mars Reconnaissance Orbiter (MRO) Mars Color Imager (MARCI) instrument has been observing Mars since 2006, providing over five-and-a-half martian years of daily observations with near global coverage. We have used this dataset to generate a time series of mosaics of the martian surface, using the extensive imaging coverage to produce composites that are largely free of cloud cover and close to the 1 km/pixel spatial scale of the instrument along its center track. These mosaics have allowed us to investigate and constrain the seasonality of albedo changes that result from the redistribution of surface dust by aeolian processes. We find that many regions of the planet have seasonal cycles of dust deposition and erosion, but others show secular variations or multi-annual trends that alter the visible appearance of the planet on timescales that are comparable to or longer than the present dataset. Changes take place both following observable dust storms and in their absence, depending on location and season. Dust settling associated with seasonal atmospheric opacity declines provides an important reset to regions that experience significant dust removal. Detailed characterizations of the surface dust behavior of different regions provided here represent a portion of the global dust cycle (an important element of the martian climate system) and provide observational constraints for regional- and global-scale climate models. In addition, seasonal and longer-term variations in the surface dust cover have important implications for future remote sensing and human exploration efforts.