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 availabilityPhyllosilicate alteration in ancient terrains in association with unaltered crust

6 Candidate sites evaluateda) Nili Fossae Troughb) Nilosyrtis layered depositsc) Eroded Noachian basementd) Delta deposite) Olivine-phyllosilicatef) 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

OlivineLow-Ca PyroxenePhyllosilicate

a

b

c d

e f

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

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THEMIS VIS V02444003

MOC E1200555

MOC E1200555

THEMIS VIS V14576022

MOC R1403073

• 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

MOC M2101233

THEMIS VIS V10333012

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

• 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

-650 to -600 km elevation