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Home , Nili Fossae

/Phyllosian Stratigraphy in Jack Mustard, Nili Fossae Bethay Ehlmann, and CRISM Team

Spectral Geomorphic Diversity of Noachian/Phyllosian Environments (Hydrothermal, alluvial/fluvial, shallow crust/pedogenic) Distinct relationships among: Impact ejecta volcanics Phyllosilicate-bearing infill of Nili Fossae Strongly altered Noachian crust Unaltered Noachian crust Noachian crust enriched in low- Ca Noachian crust enriched in 1 phyllosilicate Nili Fossae Geologic Highlights

• Noachian Habitable Environments Regional deposit

– Ancient crustal and genesis region Widespread Gradation – Fluvially transported sediments

– Hydrothermal systems Fluvial Processes • Impact processes Trough development Carbonate deposit – Superbly exposed ejecta Phyllosilicate Formation from 65 km crater Isidis Impact Syrtis Major – Ejecta blocks in a phyllosilicate- 3.96 Ga Unit Volcanism bearing matrix Time – Transport, fluidization, alteration • Composition and character of ancient, unaltered crust • Composition, mineralogy, and texture of Hesperian Syrtis Major lava • Traverse the Noachian-Hesperian Boundary 2 3 Regional Mineral Assemblages, Nili Fossae

Ehlmann et al., 2008; JGR 2009 Minerals in context with observation ID’s and coordinates

Fe/Mg smectite kaolinite illite/muscovite chlorite hydrated Si-OH analcime (zeolite) Carbonate Other zeolite/sulfate Serpentine Prehnite 4 Olivine Low-Ca Pyroxene Phyllosilicate Fe-Phyllosilicate

FRT000064D9

5 FRT000064D9: 2.4, 1.8, 1.15 μm RGB

Mineralogy identified Fe-oxide and crystalline hematite Fe/Mg Smectite with variety of

band positions, H2O content Kaolinite Carbonate Pyroxene (Low and High Ca) 6 Olivine FRT000064D9: 2.4, 1.8, 1.15 μm RGB

Mafic mineralogy estimated with MGM model.

Blue=High-Ca pyroxene band strength = Low-Ca pyroxene band strength Both stretched 0.02-0.12

7 FRT000064D9: 2.4, 1.8, 1.15 μm RGB

Mafic mineralogy estimated with MGM model.

Blue=High-Ca pyroxene band strength Green= Low-Ca pyroxene band strength Both stretched 0.02-0.12

8 0.26 1.1

FRT000064D9: 0.24 Low-Ca Pyroxene OLINDEX-2 R Phyllosilicate 1.05 0.22 LCP-mgm G Fe-Phyllosilicate 0.2 BD1900 B Ratio 1 Ratio 0.18

0.16 0.95 141 388 5x5 Volcano Scan Corrected Albedo 0.14 141 28 5x5

0.12 0.9 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6

Wavelength

Dune fields show evidence for a weak olivine absorption Note that pyroxene bands are apparent in the Lambert albedo spectra

9 FRT000064D9: 1.1 0.12 0.1 1.08 0.08 Red-Blue Ratio 0.06 Lambert Albedo 920 Band (LCP) 1.06 540 Band (Hematite) 0.04

1.04 0.02 Relative Reflectance

0 1.02 -0.02 Laboratory, Hematite 1 -0.04 0.4 0.5 0.6 0.7 0.8 0.9 1

Wavelength Red crystalline hematite is observed in discrete regions of the material filling the trough floor

10 0.2 FRT000064D9: Low-Ca Pyroxene OLINDEX-2 R Phyllosilicate 0.18 LCP-mgm G Fe-Phyllosilicate BD1900 B 0.16

0.14 Relative Reflectance

457 95 5x5 0.12 457 204 5x5 320 215 5x5 320 322 15x5

0.1 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6

Wavelength Fe-Mg phyllosilicate indicated by absorptions near 2.3, 1.91, and 1.41 μm

Spectra ratioed to brown- colored dunes

11 FRT000064D9: 1.2 Low-Ca Pyroxene OLINDEX-2 R Phyllosilicate LCP-mgm G Fe-Phyllosilicate 1.1

BD1900 B 1

0.9 Relative Reflectance

0.8

0.7 11.522.533.54

Wavelength Fe-Mg phyllosilicate indicated by absorptions near 2.3, 1.91, and 1.41 μm

Possible absorption near 3 μm

due to H2O

12 1.24 FRT000064D9: Low-Ca Pyroxene 1.2 OLINDEX-2 R Phyllosilicate LCP-mgm G Fe-Phyllosilicate 1.16 BD1900 B 1.12

1.08

1.04 Relative Reflectance

1

0.96

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6

Wavelength Fe-Mg phyllosilicate indicated by absorptions near 2.3, 1.91, and 1.41 μm

The spectral properties of Fe/Mg phyllosilicates is relatively consistent across scene but with small variance in 13 the 1.9 μm H2O band 0.24 1.1 FRT000064D9: 1.41 1.916 2.30 Low-Ca Pyroxene 0.22 OLINDEX-2 R Phyllosilicate 1.05 Fe-Phyllosilicate LCP-mgm G 0.2

BD1900 B Ratio 0.18 1 Ratio

0.16

0.95 196 94 5x5

Volcano Scan Corrected Lambert Albedo 0.14 196 17 5x5

0.12 0.9 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6

Wavelength

Fill of Nili Fossae floor shows definitive absorptions for hydrated silicate, consistent with Fe/Mg smectite clay

14 FRT000064D9: R=2.4 G=1.8 B=1.08 μm 1.15 1

0.9

1.1 0.8 Reflectance

0.7 Ratio

1.05 0.6

Ratio

CCJB25 0.5

1 0.4 11.522.5

Wavelength Small outcrops on the plateau show distinct absorptions diagnostic of kaolinite

15 FRT000064D9: R=2.4 G=1.8 B=1.08 μm 1.15 1

0.9

1.1 0.8 Reflectance

0.7 Ratio

1.05 0.6

Ratio

CCJB25 0.5

1 0.4 11.522.5

Wavelength Small outcrops on the plateau show distinct absorptions diagnostic of kaolinite

16 FRT000064D9: R=2.4 G=1.8 B=1.08 μm 0.25 1.1

1

0.2 Relative Reflectance 0.9

Reflectance 0.8 0.15

0.7

0.1 0.6 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6

Wavelength

2500 nm Band, may be indicative of carbonate but careful analysis required Small blocks show possible carbonate (Blue ratio spectrum) Larger region is not consistent with carbonate (black ratio spectrum) 17 1.1 1.6 FRT000064D9: R=2.4 G=1.8 B=1.08 μm Possible Carbonate 1.5

1.05 1.4

1.3

1

1.2

1.1

Relative Reflectance 0.95

1

0.9 0.9 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 Wavelength

2500 nm Band, may be indicative of carbonate but careful analysis required Small blocks show possible carbonate (Blue ratio spectrum) Larger region is not consistent with carbonate (black ratio spectrum) 18 3 km 500 m Blocks with possible carbonate signature

Unaltered Noachian crust embedded in phyllosilicate-bearing formation

HiRISE Color

Layered Low-Ca Pyroxene Sediments Phyllosilicate Fe-Phyllosilicate 19 Olivine Low-Ca Pyroxene Phyllosilicate Fe-Phyllosilicate

20 Scarp walls Noachian crust Channel floor Trough fill Hesperian lava Hargraves Ejecta Fresh Craters

21 Hargraves Ejecta Syrtis Lava Hesperian

Smectite-bearing Fossae Fill Smectite-bearing Fossae Fill Smectite-rich Noachian Crust LCP-rich Noachian Crust

(Representative vertical and horizontal distances, not to scale) 22 Nili Fossae Trough • Distinct morphologic units with broad mineralogic diversity • Careful analysis of mineral indicators through spectral analysis required for validation and verification • Can be validated to the level of a few pixels (e.g. breccia blocks) • Regional geology indicates sustained interaction of water with the crust over an extended period as a consequence of multiple episodes of distinct character – Fe/Mg Phyllosilicates with variation in band position, strength of water absorption – Smectite clay transported and deposited in fluvial systems – Regional episode of kaolinite formation – Carbonate formation in association with olivine – Chlorite, zeolite, and hydrated silicate in association with impacts • Hesperian volcanics show no evidence for extensive alteration 23