Quantified Aeolian Dune Changes on Mars Derived From Repeat Context Camera Images

Aeolian systems are active across much of the surface of Mars and quantifying the activity of bedforms is important for understanding the modern and recent Martian environment. Recently, the migration rates and sand fluxes of dunes and ripples have been precisely measured using repeat High Resolution Imaging Science Experiment (HiRISE) images. However, the limited areal extent of HiRISE coverage means that only a small area can be targeted for repeat coverage. Context Camera (CTX) images, although lower in spatial resolution, have wider spatial coverage, meaning that dune migration can potentially be monitored over larger areas. We used time series, coregistered CTX images and digital elevation models to measure dune migration rates and sand fluxes at six sites: Nili Patera, Meroe Patera, two sites at Herschel crater, McLaughlin crater, and Hellespontus Montes. We observed dune displacement in the CTX images over long-term baselines (7.5-11 Earth years; 4-6 Mars years). Bedform activity has previously been measured at all these sites using HiRISE, which we used to validate our results. Our dune migration rates (0.2-1.1 m/EY) and sand fluxes (2.4-11.6 m(3) m(-1) EY-1) compare well to measurements made with HiRISE. The use of CTX in monitoring dune migration has advantages (wider spatial coverage, faster processing time) and disadvantages (ripples not resolved, digital elevation model dune heights may be underestimates); the future combined use of HiRISE and CTX is likely to be beneficial. Plain Language Summary Sand dunes and ripples are present across much of the surface of Mars. The motion of both dunes and ripples has been observed from orbital satellite images and rovers on the surface, which shows that the environment is constantly changing. Previously, high-resolution (submeter scale) satellite images have been used to track the movement of dunes and ripples across the surface, which generally move at rates of up to several meters per year. However, the limited coverage of high-resolution images means that only select sites can be monitored. Here we use medium resolution (meter scale) satellite images, which covers a much wider area, as a test case to see if we can accurately measure the movement of dunes, which are typically several hundred meters in length. We chose six sites that have previously been measured using high-resolution images to monitor of over periods of similar to 10 Earth years. Our results show that our dune migration rates generally compare well to the high-resolution measurements. The combined future use of medium and high-resolution images for monitoring dunes on Mars is likely to be beneficial.