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Semi-Automatic Yardang Morphometry Reveals Similar Formation Processes in the Medusae Fossae Formation, Mars and the Altiplano-Puna, Argentina

Presentation #308.02 in the session “Mars Surface/Atmosphere Interactions”.

Published onOct 26, 2020
Semi-Automatic Yardang Morphometry Reveals Similar Formation Processes in the Medusae Fossae Formation, Mars and the Altiplano-Puna, Argentina

Yardangs are common eolian erosional landforms on Mars with numerous analog landforms in deserts on Earth. They have streamlined forms created by the abrasion and deflation of consolidated substrates under mostly unimodal wind regimes. Recent geomorphologic studies have semi-automatically identified yardangs in topographic data of Iran (Ehsani and Quiel, 2008) and California (Pelletier et al., 2018). This work uses a model adapted from Pelletier et al., 2018 to do the same for yardangs in Argentina and on Mars, comparing the shapes and sizes of a yardang fleet from each location. After visually determining appropriate constraints for seeding the model, we use uniform standards to compare distinct yardang fleets, including terrestrial analogs with in-situ datasets. This aids the interpretation of wind conditions and substrate properties in areas of Mars with yardangs. The model inputs are HiRISE DTM DTEEC_009175_1810_009808_1810_A01 (McEwen et al., 2007) for the Martian fleet and a drone imagery derived DTM for the Earth fleet. Yardang boundaries are projected along the median elevation contour within an area of seed pixels. The elevation criterion gives consistent results across regions despite different seed criteria, such as high slopes on Mars and high curvature (i.e. high change in slope) for the Earth yardangs, which have reentrant prows. From the resulting datasets we find yardang spacing, length, width, and height, which we use to identify variability in yardang properties within the fleet and to make comparisons between yardangs forming in other locations under different conditions. The Mars yardangs are formed from the stratigraphically lowest of three geologic units in the northwest part (146° E, 1° N) of the Medusae Fossae Formation (MFF). They generally have “whaleback” medial ridges and appear to lack reentrant prows at HiRISE resolution (25 cm/pixel). The 30 km2 area contains 5983 yardangs, with a median size of 52 m2, covering 62% of the area. In contrast, the 5 km2 area in Argentina contains 2728 yardangs, with a median size of 16 m2, covering 12% of the area. The median area of the MFF yardangs is thus ~3x greater, with some outliers >1 km2. These large outliers may include the harder, caprock-like middle MFF member. The median spacing between yardangs was also 3x greater in the MFF than in the Altiplano-Puna, suggesting a similar balance between eolian weathering and erosion resistance for both places, but with differences in magnitude. Applying this technique to additional yardang fleets can help identify the fundamental processes controlling the scale of yardang forms on both Earth and Mars.

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