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Latitudinal Trend of Roughness and Circumpolar Mantles on Mars

Latitudinal Trend of Roughness and Circumpolar Mantles on Mars. M. A. Kreslavsky J. W. Head III Brown University. Statistical characterization of kilometer-scale topography with MGS MOLA data. MOLA - measurements of the surface elevation: ~ 600 000 000 shots

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Latitudinal Trend of Roughness and Circumpolar Mantles on Mars

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  1. Latitudinal Trend of Roughnessand Circumpolar Mantles on Mars M. A. Kreslavsky J. W. Head III Brown University

  2. Statistical characterization of kilometer-scale topography with MGS MOLA data • MOLA - measurements of the surface elevation: • ~ 600 000 000 shots • 0.3 km shot-to-shot distance along track • up to 1.5 km gaps between tracks • up to 0.3 m vertical precision • up to 3 m vertical accuracy M. A. Kreslavsky, J. W. Head (2000) JGR-Planets, v. 105, no. E11, p. 26,695 - 26,711 + some new results

  3. d characterizes profile curvatureat given pointat given baseline. We calculated d for each shotand binned into map cells Map grid: 8x8 cells per degree. Typically ~40-80 shots per map cell Baselines used: 0.6 km2.4 km9.6 km

  4. Curvature-frequency distribution:a statistical characteristic of topographic pattern For each map cellwe calculated interquartile widthof the distribution. It characterizesroughness at given baselinefor given map cell. All map cells form a roughness mapfor each baseline We combined 3 maps for 3 baselines into one color map Baselines used: 0.6 km2.4 km9.6 km

  5. Roughness map Blue 0.6 km baseline Green 2.4 km baseline Red 9.6 km baseline Brighter = Rougher

  6. Roughness map • Olympus Mons Aureole: very rough • Amazonis and Elysium Planitia: very smooth • Dune fields: rough at small scale, flat in large scale • Polar caps: smooth at small scale; steep larger-scale slopes • Volcanic plainsare smootherthan highlands • Northern lowlands are rather smooth and have characteristic 3-km-scale roughness

  7. Latitudinal trend of roughness S hemisphere: highlands at low latitudes are rougher (30N - 30S) highlands at high latitude are smoother (>60S) at 0.6 km baseline N hemisphere: Similar trend partly masked with the dichotomy boundary and other intrinsic roughness contrasts. Interpretationthat survived tests with high-resolution MGS MOC images:Manifestation of unique type of surface mantle depositswith specific meter-scale texture

  8. MGS MOC image M03/04333 The deposits with specific fine texture (center)are superposed over underlying topography at 47N in Utopia Planitia 500 m

  9. MGS MOC image M23/01695 Dark dunes travel over the deposits with specific texture at ~75N and leave no traces. The deposits are strong, probably cemented 500 m

  10. MGS MOC image M02/01316 The deposits with specific texture show complex stratigraphy.The uppermost layer 4 m thick is removed in some places. Circular features are impact craters of cratered cones, degraded and mantled. 500 m

  11. High-latitude surface mantle deposits: • Very likely cemented by water ice • May be desiccated at lower latitudes (30-60) (Mustard et al., 2001) • Currently undergoing slow degradation at margins (?) (Mustard et al., 2001) • > 1-3 m thick ( <= roughness signature) • ~3 m thick at margins ( <= MOC images, Mustard et al., 2001)

  12. High-latitude surface mantle deposits: • Diverse morphology • Complex stratigraphy • History of successive deposition and removal • Persisted through at least Late Amazonian • Undergo changes during obliquity cycles • A range of processes operating ( <= MOC high-resolution images)

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