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

Abstract

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 m3 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.

Megaripple Migration on Mars

“…Such a crestline arrangement indicates dune‐shaping winds are mainly blowing from the north. Dunes are 11 m tall on average and up to 300 m in length (Davis et al, 2019). Colocated with the dunes, megaripples with variable albedo are visible upwind and in between dunes (Figures 3c, 7b, and 7c).…”

“…Migration vectors were then converted to flux vectors by multiplying the migration rates to the dune heights derived from HiRISE digital terrain models (DTMs) at the slip face brink heights following the method of Urso et al (2018) leading to the dune crest fluxes in m 3 m −1 yr −1 as defined by Vermeesch and Drake (2008). Note that this method of computing total sand fluxes, avoiding to track small slipfaceless dunes (Davis et al, 2019), is different than other authors and is not directly comparable (Bridges et al, 2012a;Chojnacki et al, 2018Chojnacki et al, , 2019. The process of orthorectification of the monitoring images was performed in SOCET SET® BAE Systems photogrammetry software (Kirk et al, 2008) following well established methods and procedures (Chojnacki et al, 2018).…”

“…McLaughlin crater is an ~2‐km‐deep Noachian impact basin situated at the dichotomy boundary SE of Chryse Planitia (Figure 2c). Dunes and megaripples are accumulated in the southern portion of the crater floor by dominant winds from the N in an area of increased surface roughness due to the ejecta deposit of an ~25‐km crater nearby (Figure 2d) (Davis et al, 2019). By analyzing a series of multitemporal High Resolution Imaging Science Experiment (HiRISE) images (McEwen et al, 2007) (Table 1), we test the hypothesis that megaripples associated with active dunes could be active in the present‐day atmospheric setting.…”

Measuring Ripple and Dune Migration in Coprates Chasma, Valles Marineris: A Source to Sink Aeolian System on Mars?

“…The variation in crest length and dune lengths, with linear dunes that evolve into a chain of barchans toward the rear of the dune field is observed elsewhere on Mars in relatively sediment starved regions; Davis, Banham, et al. (2020). Linear dunes are observed in our study region, and require a bidirectional wind regime (e.g., Gao et al., 2015; Tsoar, 1989), which in this case could be due to katabatic winds traveling down the canyon slopes combining with winds traveling eastwards through the valley.…”

Transverse Aeolian Ridge Growth Mechanisms and Pattern Evolution in Scandia Cavi, Mars

“…The resulting volumetric crest sand fluxes are 1.96 ± 0.20 and 1.40 ± 0.18 m 3 /m/yr, respectively. These values are on the low end, but not unusual, for actively migrating martian dunes (Bridges et al, 2013;Chojnacki et al, 2019;Davis et al, 2020). The crest sand fluxes are an order of magnitude or more lower than those measured at the Olympia Undae margin ∼200 km to the northwest (Chojnacki et al, 2019;Boazman et al, 2020), despite the study dunes' location at the windward edge of the dune field, where sand fluxes are typically at a maximum (e.g., Jerolmack et al, 2012).…”