Measurement of Bedding Geometry of Upper Aeolis Mons, Gale Crater, Mars

Abstract:

Aeolis Mons, informally called “Mount Sharp,” is a >5 km tall mound of layered sedimentary rock in Gale crater. The mound can be divided into lower and upper formations, with a clear unconformity between the two formations identified by Malin and Edgett (2000). Multiple authors (e.g. Anderson and Bell, 2010; Thomson et al., 2011; Wray, 2012) have noted that the upper formation may have a distinct origin from the lower mound. Although the Curiosity rover is expected to explore the base of the lower formation, the upper portion of Aeolis Mons is likely unreachable. HiRISE observations of the upper formation reveal sinuous bedding patterns on a scale of 100s of meters with apparent truncations. These patterns have been interpreted to be cross-beds (Anderson and Bell, 2010). However, identifying cross-bedding in orbital images is not always straightforward. Planar beds intersecting eroded topography can produce complex patterns of exposed bedding that may look superficially like cross-bedding. To confirm the presence of cross-bedding, the exposure must be studied in three dimensions.

We present initial results of an investigation using a HiRISE Digital Terrain Model (DTM) based on the HiRISE stereo pair PSP_001620_1750 and PSP_001422_1750 test the hypothesis that the upper formation of Aeolis Mons represents aeolian cross-bedding. By tracing the intersection of the beds with a plane, we will determine whether the observed patterns might be explained by the interaction of planar beds and complex erosion or if the observed structures require cross-bedded deposits. These measurements are ongoing. If the complex bedding patterns observed in the upper formation are confirmed to be cross-beds, we will present measurements of the bedding orientation and use computer models to interpret the depositional conditions for the upper formation of Aeolis Mons.

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Thomson, B.J., et al. 2011. Icarus 214, 413–432. doi: 10.1016/j.icarus.2011.05.002

Wray, J.J., 2012. Int. J. Astrobiol. 12, 25–38. doi: 10.1017/S1473550412000328