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Daytime IR contrasts

Geologic Units In Gusev Crater Ross Irwin Center for Earth and Planetary Studies National Air and Space Museum Smithsonian Institution 4th MER Landing Site Workshop January 9, 2003. THEMIS I00881002 32 km across. Daytime IR contrasts. MDIM/Daytime THEMIS. Dust devil tracks

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Daytime IR contrasts

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  1. Geologic Units In Gusev CraterRoss IrwinCenter for Earth and Planetary StudiesNational Air and Space MuseumSmithsonian Institution4th MER Landing Site Workshop January 9, 2003

  2. THEMIS I00881002 32 km across Daytime IR contrasts MDIM/Daytime THEMIS • Dust devil tracks • Gardened crater floor • Ejecta of larger craters • Etched areas

  3. MOC E17-00827, 3.76 km across High-inertia material exposed in etched terrain

  4. GUSEV CRATER STRATIGRAPHY • Duricrust or cap layer in low-inertia material; composed of or mantled by fine sediments • Low-inertia layer, gardened and etched • High-inertia layer(s) in ejecta and etched terrain • ~1 km Ma’adim deposit beneath surface layers

  5. CONTRASTS BETWEEN COARSE AND FINE LAYERS THEMIS IR I00856001 32 km across 18 km across MOC E02-00665 and E03-01511, 5.8 km across

  6. Etched terrain IR contrasts are due to material differences, not illumination THEMIS IR I00856001 32 km across 18 km across THEMIS night IR I01149002, 17 km across

  7. DURICRUST OR CAP LAYER • Crater fill preserved as positive relief • Sharp transition to gardened plains • Isolated mesas • Some elongation but L:W of knobs < 4:1 MOC E05-00471, 3 km across

  8. Fill of interior craters has lower populations IMPACT GARDENING 100m contour MOC NA E18-00950 3.5 km across MDIM/Daytime THEMIS

  9. DUST DEVIL TRACKS MDIM/Daytime THEMIS MOC E10-02768 3 km across MOC E15-00362 3 km across

  10. TESTABLE HYPOTHESES: Coarse layer • Exposure within the landing ellipse is limited; most common exposures are in crater ejecta • Composition, size, sorting, rounding? Could be fluvial deposit from Ma’adim, intracrater fluvial deposit, duricrust, or volcanic material. Magnetic? Use imagers, APXS, Mini-TES

  11. TESTABLE HYPOTHESES: Fine layer • Extensive within the landing ellipse & ejecta of small craters • Composition, size, sorting, rounding? Scale of layering? Crossbeds? Vertical sorting? Could be varves, pyroclastic, other airfall • Use imagers, APXS, Mini-TES MOC E17-00827, 3.76 km across

  12. TESTABLE HYPOTHESES: Duricrust (?) and dust devils • Presumably extensive within the landing ellipse • Are dust devils transporting a lag material? If so, what is its composition, size, etc.? What material is being exposed in the tracks? • What cement is responsible for crust (if any)? Strength properties (RAT): how well cemented?

  13. TESTABLE HYPOTHESES: Weathering • Studies of weathering on Mars have remained largely theoretical. If fluvial or lacustrine deposits are identified, are they chemically altered or the products of physical weathering and rapid transport? This has implications for paleoclimate. Is active physical or chemical weathering observed? • Use Mini-TES, APXS, and Mossbauer for sediment composition information

  14. MOC E05-01183 3 km across MOC E10-02784 3 km across ANALOG STUDIES Dichotomy boundary sediments THEMIS I00957001 32 km across

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