Rationale for Hematite Sites Mineralogy and petrology provide critical inputs to interpreting...
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Rationale for Hematite SitesRationale for Hematite Sites
• Mineralogy and petrology provide critical inputs to
interpreting geologic processes
• Volcanic, lacustrine, chemical precipitation, aeolian, etc
• All mineralogic data point to:
• A Mars dominated by volcanic processes
• Very little chemical weathering
• No evidence for carbonates or significant clays
• Presence of crystalline hematite signature argues for unique
chemical process with high probability of water
• Mineralogy and petrology provide critical inputs to
interpreting geologic processes
• Volcanic, lacustrine, chemical precipitation, aeolian, etc
• All mineralogic data point to:
• A Mars dominated by volcanic processes
• Very little chemical weathering
• No evidence for carbonates or significant clays
• Presence of crystalline hematite signature argues for unique
chemical process with high probability of water
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Global Mineral Mapping SummaryGlobal Mineral Mapping Summary
• Dust-free surfaces are volcanic materials
• Olivine detected in local regions
• No evidence for carbonates
• Unweathered to weakly weathered volcanic compositions
(basalt to andesite)
• Except for hematite sites, mineralogy of other regions likely
to be dominated by volcanic materials
• Dust-free surfaces are volcanic materials
• Olivine detected in local regions
• No evidence for carbonates
• Unweathered to weakly weathered volcanic compositions
(basalt to andesite)
• Except for hematite sites, mineralogy of other regions likely
to be dominated by volcanic materials
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Sinus Meridiani Geologic SettingSinus Meridiani Geologic Setting
• Basaltic rock with 10-15% hematite
• Layered, friable, stripped deposits
• In-place rock unit
• Hematite-rich unit is stratigraphically above cratered
highlands
• Regional tilting by Tharsis Uplift (Phillips et al.)
• Saturated population of ghost craters implies ancient
surface (Hartmann and others)
• Distinct population of young craters suggests recent
exhumation (Hartmann and others)
• Basaltic rock with 10-15% hematite
• Layered, friable, stripped deposits
• In-place rock unit
• Hematite-rich unit is stratigraphically above cratered
highlands
• Regional tilting by Tharsis Uplift (Phillips et al.)
• Saturated population of ghost craters implies ancient
surface (Hartmann and others)
• Distinct population of young craters suggests recent
exhumation (Hartmann and others)
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Hematite Formation MechanismsHematite Formation Mechanisms
I) Chemical Precipitation - Extensive near-surface water
1) Precipitation from ambient, Fe-rich water (oxide iron
formations)
2) Precipitation from hydrothermal fluids
3) Low-temperature dissolution and precipitation through
mobile ground water leaching
4) Surface weathering and coatings
II) Thermal oxidation of magnetite-rich lava
Christensen et al. 2000
I) Chemical Precipitation - Extensive near-surface water
1) Precipitation from ambient, Fe-rich water (oxide iron
formations)
2) Precipitation from hydrothermal fluids
3) Low-temperature dissolution and precipitation through
mobile ground water leaching
4) Surface weathering and coatings
II) Thermal oxidation of magnetite-rich lava
Christensen et al. 2000
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Ambient Aqueous ProcessesAmbient Aqueous ProcessesAmbient Aqueous ProcessesAmbient Aqueous Processes
• Precipitation from standing water:
(Christensen et al. 2000)
Pro Con
• Layered, friable units • Goethite not hematite
• Aram and Ophir are basins • Requires dehydration
or
recrystalization
• Precipitation from standing water:
(Christensen et al. 2000)
Pro Con
• Layered, friable units • Goethite not hematite
• Aram and Ophir are basins • Requires dehydration
or
recrystalization
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Hydrothermal ProcessesHydrothermal ProcessesHydrothermal ProcessesHydrothermal Processes
• Circulation of water through rock or saturated sediments:
(Christensen et al. 2000)
Pro Con
• Precipitation of hematite • Lack of heat source
• Evidence of water at other sites
• Evidence of sediments
• Circulation of water through rock or saturated sediments:
(Christensen et al. 2000)
Pro Con
• Precipitation of hematite • Lack of heat source
• Evidence of water at other sites
• Evidence of sediments
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Igneous ProcessesIgneous ProcessesIgneous ProcessesIgneous Processes
• Igneous Intrusion/Ignimbrite:
(Noreen et al. 2000)
Pro Con
• Layered units possibly tuffs • Requires unique
• Friable deposits volcanic composition
• Basalt compositoin • Source region
• Igneous Intrusion/Ignimbrite:
(Noreen et al. 2000)
Pro Con
• Layered units possibly tuffs • Requires unique
• Friable deposits volcanic composition
• Basalt compositoin • Source region
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Ash IndurationAsh IndurationAsh IndurationAsh Induration
• Indurated volcanic airfall:Indurated volcanic airfall:
(Hynek et al. 2001)
Pro Con
• Widespread bright and dark • Hematite formation
layered deposits mechanism unclear
• Highly friable ash • Basalt composition
• Regional/global correlations • Source regions?
• Indurated volcanic airfall:Indurated volcanic airfall:
(Hynek et al. 2001)
Pro Con
• Widespread bright and dark • Hematite formation
layered deposits mechanism unclear
• Highly friable ash • Basalt composition
• Regional/global correlations • Source regions?
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Other MechanismsOther MechanismsOther MechanismsOther Mechanisms
• Low-temperature dissolution and precipitation through
mobile ground water leaching
• Requires extensive surface water - no other
morphologic evidence
• Surface weathering and coatings
• Appears unlikely due to excellent correlation with
geologic units
• Typically produces red, not gray, hematite
• Low-temperature dissolution and precipitation through
mobile ground water leaching
• Requires extensive surface water - no other
morphologic evidence
• Surface weathering and coatings
• Appears unlikely due to excellent correlation with
geologic units
• Typically produces red, not gray, hematite
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Testable Hypotheses: What Will MER Payload Do?
Testable Hypotheses: What Will MER Payload Do?
• Lacustrine
• Sedimentary structures, sorting, bedding, grain size
• Pancam, Microscopic Imager
• Major and minor component mineralogy
• Mini-TES, APXS, Mossbauer, Pancam
• Hydrothermal
• Mineralogy, alteration
• Pancam, Microscopic Imager
• Precipitation, veins, cements
• Pancam, Microscopic Imager
• Lacustrine
• Sedimentary structures, sorting, bedding, grain size
• Pancam, Microscopic Imager
• Major and minor component mineralogy
• Mini-TES, APXS, Mossbauer, Pancam
• Hydrothermal
• Mineralogy, alteration
• Pancam, Microscopic Imager
• Precipitation, veins, cements
• Pancam, Microscopic Imager
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Testable Hypotheses: What Will MER Payload Do?
Testable Hypotheses: What Will MER Payload Do?
• Igneous
• Large- and small-scale volcanic structures
• Pancam, Microscopic Imager
• Mineralogy
• Mini-TES, APXS, Mossbauer, Pancam
• Indurated airfall
• Grain size, rounding, sorting, bedding
• Pancam, Microscopic Imager
• Glass and ash vs. basaltic grains
• Mini-TES
• Minor mineralogy
• APXS, Mossbauer
• Igneous
• Large- and small-scale volcanic structures
• Pancam, Microscopic Imager
• Mineralogy
• Mini-TES, APXS, Mossbauer, Pancam
• Indurated airfall
• Grain size, rounding, sorting, bedding
• Pancam, Microscopic Imager
• Glass and ash vs. basaltic grains
• Mini-TES
• Minor mineralogy
• APXS, Mossbauer
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SummarySummarySummarySummary
• Presence of unique hematite mineralogy has led to formulation of multiple testable hypotheses
• Most hypotheses involve significant amounts of liquid water
• Mineralization requires long-term stability of liquid water near surface
• Time is critical to origin and survival of life
• Hematite sites are only locations on Mars with proven occurrence of a possible water-related mineralogy
• Layered friable deposits occur in all hematite sites
• Suggests sedimentary origin
• More likely to preserve products and record of early abiotic or biotic environments than volcanic, impact, metamorphic, or erosional environments
• Presence of unique hematite mineralogy has led to formulation of multiple testable hypotheses
• Most hypotheses involve significant amounts of liquid water
• Mineralization requires long-term stability of liquid water near surface
• Time is critical to origin and survival of life
• Hematite sites are only locations on Mars with proven occurrence of a possible water-related mineralogy
• Layered friable deposits occur in all hematite sites
• Suggests sedimentary origin
• More likely to preserve products and record of early abiotic or biotic environments than volcanic, impact, metamorphic, or erosional environments