Presentation Information
[PPS07-P02]Resolution-Aware Analysis of Gravity-Referenced Slopes on Phobos: Implications for Surface Processes and Landing-Site Assessment
*Ryodo Hemmi1, Hiroshi Kikuchi2 (1.Japan Aerospace Exploration Agency, 2.Gakushuin University)
Recent global polyhedral shape models of Phobos achieve mean facet edge lengths of ~18 m, enabling detailed computation of gravity-referenced slope magnitude and downslope azimuth. While increasing geometric resolution is generally assumed to improve topographic analysis, it remains unclear to what extent higher-resolution models alter geomorphically meaningful slope diagnostics, particularly in the context of mass wasting and landing-site evaluation.
In this study, we compute slope angle and aspect relative to the local effective gravity vector using the highest-resolution currently available global shape model of Phobos (Ernst et al., 2023). We analyze global slope distributions, circular statistics of aspect, and regional patterns associated with crater walls and previously reported mass-wasting features. To assess scale dependence, we evaluate the stability of slope and aspect fields under spatial aggregation, distinguishing facet-scale roughness from regionally coherent gravity-controlled gradients.
Our preliminary results indicate that while local facet normals vary with increasing geometric detail, regional-scale slope orientations exhibit convergence above a characteristic spatial scale. Areas persistently identified as steep and directionally coherent are spatially associated with geomorphic settings linked to downslope transport. These findings are consistent with an interpretation that gravity-controlled slope structure on Phobos may be governed primarily by regional-scale topography rather than meter-scale surface roughness.
From an exploration perspective, this implies that slope-based hazard assessments and preliminary landing-site screening for missions such as MMX can be performed using existing global shape models while explicitly quantifying their limitations and uncertainty bounds, thereby providing guidance on when higher-resolution local DEMs become necessary. High-resolution models remain essential for characterizing local microtopography and discrete hazards; however, their added value for gravity-referenced slope orientation must be evaluated within a scale-aware framework.
References
Ernst, C. M., Daly, R. T., Gaskell, R. W., et al. (2023), High-resolution shape models of Phobos and Deimos from stereophotoclinometry, Earth, Planets and Space, 75, 103. https://doi.org/10.1186/s40623-023-01814-7
In this study, we compute slope angle and aspect relative to the local effective gravity vector using the highest-resolution currently available global shape model of Phobos (Ernst et al., 2023). We analyze global slope distributions, circular statistics of aspect, and regional patterns associated with crater walls and previously reported mass-wasting features. To assess scale dependence, we evaluate the stability of slope and aspect fields under spatial aggregation, distinguishing facet-scale roughness from regionally coherent gravity-controlled gradients.
Our preliminary results indicate that while local facet normals vary with increasing geometric detail, regional-scale slope orientations exhibit convergence above a characteristic spatial scale. Areas persistently identified as steep and directionally coherent are spatially associated with geomorphic settings linked to downslope transport. These findings are consistent with an interpretation that gravity-controlled slope structure on Phobos may be governed primarily by regional-scale topography rather than meter-scale surface roughness.
From an exploration perspective, this implies that slope-based hazard assessments and preliminary landing-site screening for missions such as MMX can be performed using existing global shape models while explicitly quantifying their limitations and uncertainty bounds, thereby providing guidance on when higher-resolution local DEMs become necessary. High-resolution models remain essential for characterizing local microtopography and discrete hazards; however, their added value for gravity-referenced slope orientation must be evaluated within a scale-aware framework.
References
Ernst, C. M., Daly, R. T., Gaskell, R. W., et al. (2023), High-resolution shape models of Phobos and Deimos from stereophotoclinometry, Earth, Planets and Space, 75, 103. https://doi.org/10.1186/s40623-023-01814-7