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
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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’
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Silica-bearing units near landing site
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OH- H2O Si-OH
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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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