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

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

3. HiRISE: MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE 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) Loizeau et al., 2007

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

5. MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE 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

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

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

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

9. MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE 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 Loizeau et al., submitted to Icarus

10. MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE 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

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

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

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

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

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

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

17. RELATION WITH VALLEYS Loizeau et al., 2007

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

19. - 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 FORMATIONS MAWRTH VALLIS STRATIGRAPHY: THE OMEGA-HRSC PICTURE

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