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MAWRTH VALLIS STRATIGRAPHY: A COUPLED OMEGA - HRSC PICTURE

MAWRTH VALLIS STRATIGRAPHY: A COUPLED OMEGA - HRSC PICTURE. Worshop on Martian Phyllosilicates CNES/Paris, October 21-23 2008. D. Loizeau, N. Mangold, F. Poulet, V. Ansan, E. Hauber, J.-P. Bibring, Y. Langevin, B. Gondet, P. Masson, G. Neukum. LOCALISATION. Dichotomy

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MAWRTH VALLIS STRATIGRAPHY: A COUPLED OMEGA - HRSC PICTURE

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  1. MAWRTH VALLIS STRATIGRAPHY: A COUPLED OMEGA - HRSC PICTURE Worshop on Martian Phyllosilicates CNES/Paris, October 21-23 2008 D. Loizeau, N. Mangold, F. Poulet, V. Ansan, E. Hauber, J.-P. Bibring, Y. Langevin, B. Gondet, P. Masson, G. Neukum

  2. LOCALISATION • Dichotomy • Mawrth Vallis: outflow channel • Highly cratered noachian plateaus MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE Loizeau et al., 2007

  3. A BRIGHT LAYERED UNIT • Phyllosilicates in the bright material (Poulet et al., 2005; Bibring et al., 2006) • Distinct outcrops Fe/Mg or Al-phyllosilicates • - Thin layers first revealed by MOC (Malin & Edgett, 2000) MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE Loizeau et al., 2007 HiRISE:

  4. A BRIGHT LAYERED UNIT MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE Loizeau et al., 2007

  5. How to study the stratigraphy ? • Stratigraphy ? • discovered with MOC • locally studied with HiRISE • but cannot be regionally studied by following each single layers • We need another method to retrieve the regional geometry • - use of HRSC datasets MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE

  6. DIFFERENT COLORS... RGB « raw » composit 4 HRSC color channels: IR, red, green, blue MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE

  7. HRSC COLORS / OMEGA MINERALOGY Al-phyllosilicates MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE Fe/Mg-phyllosilicates

  8. HRSC COLORS / OMEGA MINERALOGY MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE

  9. COMPOSITIONAL SUB-UNITS - Layers organized (at least locally) in color sub-units (and though composition sub-units) - No progressive transition from one sub-unit to the other MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE Loizeau et al., submitted to Icarus

  10. COMPOSITIONAL SUB-UNITS Assuming composition sub-units linked to single layers  The sub-units can be the indicators for the stratigraphy  Use of HRSC colors and DTMs on the color sub-units MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE

  11. Montmorillonite + kaolinite 65% + ferrihydrite E Light colored, layered buttes Nontronite 65% + ferrihydrite W Nontronite 45% + ferrihydrite + pyroxene 5 km WESTERN OUTCROP MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE

  12. E Butte on the crater wall Light colored, layered buttes W Central butte 5 km WESTERN OUTCROP MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE

  13. Evidence for deposition on top of a paleo-surface WESTERN OUTCROP MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE Loizeau et al., submitted to Icarus

  14. CENTRAL REGION MAWRTH VALLIS STRATIGRAPHY: THE OMEGO-HRSC PICTURE

  15. CENTRAL REGION • 3 sub-units : • -> white/blue • -> yellow/red • -> blue • On a brown, altered surface. MAWRTH VALLIS STRATIGRAPHY: THE OMEGO-HRSC PICTURE Loizeau et al., submitted to Icarus

  16. RELATION WITH MAWRTH VALLIS CHANNEL Loizeau et al., submitted to Icarus Loizeau et al., 2007

  17. RELATION WITH VALLEYS Loizeau et al., 2007

  18. SUMMARY • Thickness : 200m at minimum • Unit subdivided in superimposed color/composition sub-units • exhumed paleo-surface •  deposition occurred on top of this brown unit MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE

  19. FORMATIONS • Alteration happened during or after deposition? • - Aqueous or eolian deposits? ashes? • MSL could answer this • And what is the origin of the compositional sequences? •  Variation of surface/groundwater chemistry • if alteration occurred during the deposition • brown paleosurface altered at the beginning of the deposition •  Variation of ashes/sediments composition altered in situ • if alteration occurred after deposition • brown paleosurface could be the summit of less alterable unit MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE

  20. THANK YOU FOR YOUR ATTENTION!

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