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Lunar Elephant Hide Texture Characterization

Presentation #207.01 in the session Moon & Earth II (Oral Presentation)

Published onOct 23, 2023
Lunar Elephant Hide Texture Characterization

“Hummocky” textures in the regolith are relatively common on the Moon, especially on moderately steep to gentle slopes in the lunar highlands. Informally known as “elephant hide texture” (EHT), these regolith patterns composed of meters-to-decameters-scale lobate features are best explained by downslope transport of loose regolith [1–5]. While previous workers show EHT occurs on slopes steeper than 5–8°, regardless of latitude and slope orientation [5, 6], a full understanding of the conditions necessary for the formation of EHT is still lacking.

For our study, we digitized EHT morphology at the meter scale on terrains with ancient well-developed highland soils (Pre-Nectarian to Nectarian) where EHT is most commonly observed. Using five Lunar Reconnaissance Orbiter Camera (LROC) NAC (Narrow Angle Camera) Digital Terrain Models (DTMs) spaced ~20° latitude apart, we test how EHT varies under slope and temperature regimes. We sampled 1 km2 areas (roughly 200 EHT lobes) within each NAC orthophoto where EHT was visible on slopes 1–30°. The sinuous morphology (or shadows) between lobes were mapped at the pixel scale of each orthophoto.

We compared lobe locations to the corresponding LROC NAC DTM slope map as well as overlapping low-sun (71–88° incidence) NAC images at similar pixel scales to the orthophoto to ensure the features were reproducible. The Minimum Bounding Geometry Tool in ArcMap was used to fit a rectangle around each lobe to obtain maximum length and width values. The Zonal Statistics tool was used to gather slope data from each EHT lobe.

Our preliminary data show that maximum lobe length and width ratios for EHT are similar across all latitude bins, but overall lobe size appears locally controlled. Each region has self-similar lobe size, but average lobe size varies region to region. More data collection is needed to further constrain the relationship between EHT and slope. In future work, we plan to map EHT as a function of age and composition to understand EHT variations with regolith nature and thickness.

[1] Runcorn and Urey, 1972. Springer, [2] Plescia and Robinson, 2010. EPSC, 731. [3] Plescia and Cintala, 2012. JGR Planets, 117, E12. [4] Xiao et al. 2013. Earth Planet. Sci. Lett. 376, 1–11. [5] Kreslavsky et al. 2021. LPSC 52, #1826. [6] Bondarenko et al. 2022. LPSC 53, #2469.

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