1. Aqueous Alteration and Habitability in Nili Fossae J.F. Mustard, F. Poulet, N. Mangold, J-P. Bibring, R.E. Milliken, S. Pelkey, and L. Kanner Noachian crust enriched in low-Ca pyroxene Noachian crust enriched in phyllosilicate Habitability defined by water activity, nutrient and energy availability Phyllosilicate alteration in ancient terrains in association with unaltered crust

2. 6 Candidate sites evaluated a) Nili Fossae Trough b) Nilosyrtis layered deposits c) Eroded Noachian basement d) Delta deposit e) Olivine-phyllosilicate f) Altered olivine Systematic mapping of mafic and aqueous minerals Detailed verification of aqueous detections Geologic context of major occurrences –Noachian basement –Delta deposits –Layered material Identification of Targets with OMEGA VNIR Data Olivine Low-Ca Pyroxene Phyllosilicate a b c d ef

3. Nili Fossae Trough Distinct phyllosilicate outcrops connected to geologic formations exposed in a sapping (?) channel Phyllosilicate in the distal portion of ejecta deposit showing lobate/textured morphology Adjacent unaltered basement and phyllosilicate => chemical disequilibrium Hesperian volcanics of Syrtis Major sampling a critical time-stratigraphic marker and major lithology Noachian basement enriched in low-Ca pyroxene possibly sampling primary crust

7. THEMIS VIS V02444003

9. MOC E1200555

11. THEMIS VIS V14576022

12. MOC R1403073

13. Topography: -690 to -520 m Slopes 2-5 km length scale: < 2.5° Thermal inertia: > 100 J m -2 s -0.5 K -1 Albedo: < 0.25

15. MOC M2101233 THEMIS VIS V10333012

16. Nili Fossae Trough: Habitability Water activity : Nutrients : Energy Phyllosilicate is a possible template for the origin of RNA- DNA and life Chemical sources of energy are critical Pros Phyllosilicate in bedrock and ejecta: neutral pH, concentration and preservation of organics chemical energy sources Cons Ancient (preservation) Environment from morphology complex

17. Nili Fossae region presents a number of high priority targets for MSL Numerous phyllosilicate-bearing outcrops representing several deposition/formation environments Trough site: phyllosilicate adjacent/intimate with unaltered bedrock, distal ejecta deposits rich in clay, Syrtis Major lavas Trough site meets preliminary EDL, trafficability Planetary protection requirements Importance of phyllosilicate: –Preferential sequestration of organic carbon –Formation in habitable environments with abundant energy sources and water

18. -650 to -600 km elevation