Quartz and Hydrated-Silica Bearing Terrain in Antoniadi Crater

Matt Smith & Josh Bandfield

University of Washington

NOTE ADDED BY JPL WEBMASTER: This content has not been approved or adopted by, NASA, JPL, or the California Institute of Technology. This document is being made available for information purposes only, and any views and opinions expressed herein do not necessarily state or reflect those of NASA, JPL, or the California Institute of Technology.

First Joint Rover Landing Site Workshop - February 29, 2012 1

Highlights of Antoniadi Crater Site

• Only identified quartz on the planet

* Best preserved evidence of ancient life are in chert deposits

• All quartz is co-located with hydrated silica = aqueous formation mechanism

• Phyllosilicate-bearing Noachian breccia – greater mineral diversity and regional context

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Antoniadi Crater

30 km

Isidis

BasinSyrtis

Majo

r

Nili

Fossae

Antoniadi

Crater

Quartzofeldspathic material(Bandfield et al., 2004; Bandfield 2006)

Fe/Mg smectite detections

Hydrated silica detections(Ehlmann et al., 2009)

Greeley and Guest (1987) & Skinner (2006)

Proposed landingsite

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Detecting the felsic signature

First Joint Rover Landing Site Workshop - February 29, 2012

Short wavelength features shift to longer wavelengths for less silica-rich compositions

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Quartz-bearing units near landing site

First Joint Rover Landing Site Workshop - February 29, 2012

A

A’

5

Silica-bearing units near landing site

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OH- H2O Si-OH

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First Joint Rover Landing Site Workshop - February 29, 2012

Bulk SiO2index

TIR (THEMIS) VNIR (CRISM)

hydrated silica index

Quartz and hydrated silica are in the same units!

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First Joint Rover Landing Site Workshop - February 29, 2012

TIR VNIR

TIR VNIR TIR VNIRhydrated silica index

hydrated silica index

hydrated silica index

Quartz and hydrated silica are in the same units!

Bulk SiO2index

Bulk SiO2index

Bulk SiO2index

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First Joint Rover Landing Site Workshop - February 29, 2012

Rice et al., 2012, submitted

Could the hydrated silica be crystalline?

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First Joint Rover Landing Site Workshop - February 29, 2012

modified from Rice et al., 2012, submitted

increasing crystallinity

Silica comparison: How much alteration?

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Silica comparison: How much alteration?

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A wet path to quartz

• Opal-A will alter to quartz in water

• Common diagenetic pathway for terrestrial chert deposits

• Alteration time is affected by heat, water chemistry & water availability

• Alteration can take between 1,000 (hydrothermal) – 400 million years (freezing) [Tosca & Knoll, 2009]

Lynne et al., 2005

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Source of the silica

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Sediment is eroding and being transported downslope

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Source of the silica

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Hydrated silica detections intensify as the sediment moves and accumulates downslope

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Sites of interest near landing ellipse

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Silica-bearing

Phyllosilicate-bearing

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Astrobiology: Making and trapping life

First Joint Rover Landing Site Workshop - February 29, 2012

• Forms more easily in alkaline waters = good for early life

• The exceptionally high degree of crystallinity here suggests more water/heat to allow for life to gain a foothold

• Silica precipitates quickly and can quickly entomb microfossils

Rodgers et al., 2004

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Astrobiology: Preserving the evidence

First Joint Rover Landing Site Workshop - February 29, 2012

Well-preserved microfossils from the 1.9 GaGunflint Chert, Ontario [Barghoorn and Tyler, 1965]

Silica is chemically stable over geologic timescales

Best-preserved evidence of ancient microbes are

found in proterozoic cherts

Farmer and Des Marais, 1999

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Landing ellipse parameters

• Accessibility to targets– Nearest Target: 0 km

– Ultimate Target: 13 km (from center of ellipse)

• Dust cover index: 0.97

• Latitude, Longitude: 20.568N, 62.8122E

• Rock abundance: 15.7% blocks [IRTM]

• Thermal inertia: 316 [TES]

• Albedo: 0.18 [IRTM + TES]

• Mean Elevation: 113.2 m

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Regional context

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Noachian phyllosilicates

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THEMIS spectra of QF units

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How can quartz form?

• Primary igneous mineral

• Aqueous precipitate- Diagenetic alteration of opaline silica

- Primary (veins/vugs)

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