The New Mars Synthesis NWA 7034 and Gale Crater Strata

J.E. Brandenburg

LPSC 2015

Outline

• The New Mars Synthesis

• NWA 7035 and The Mars Absolute Chronology

• The Approximate age of Gale Crater Strata

• A Geochemical Analysis of the Strata

• Implications for the presence of a past biosphere

• Summary and conclusions

Two Key Questions

1. What age are the strata?

2. What Mars conditions formed them?

The New Mars Synthesis:

• Mars has a 4x Lunar Chronology

• Mars had persistent greenhouse

• Mars Northern Ocean lasted Early Amazonian

• Mars had an Earthlike Biosphere that effected its geochemical history

• Mars suffered catastrophic climate change due to Lyot Impact

Bio-stabilized Greenhouse

• New Mars Synthesis proposes photosynthetic oxygen to chemically stabilize a CO2 and CH4 greenhouse on Mars allowing long-lived liquid ocean and terrestrial like hydrocycle

• Oxygen and oxygen produced acids recycle CO2 and preserve Greenhouse

• Free oxygen creates ozone layer allowing life to flourish : Martian Gaia

NWA 7034 and Mars Absolute Chronologies

• NWA 7034 and ALH84001 are ~4.5 Gyr old

• Other Mars meteorites are 1Gyr -.2Gyr old

• This reflects Mars dichotomy of Surface Ages

• Southern Highlands is very Old

• Northern Plains is very Young

• Gale Crater sits on boundary and thus should be of Middle Age

NWA 7034 and ALH84001 Ages

SNC Ages

4x Lunar Stratigraphy

4x lunar Chronology and Gale crater

• Rover sees top of geologic column

• Modern era erosion is much slower than past

-the north of Mars is young average ~0.5 Billion years old

-Gale crater is ~ 1 billion years Old

Gale Crater Geologic Formations

Surface Age of Sediments is Young

Gale crater sediment Approximate age

Gale crater sediments were built up in aqueous environment and then eroded Positon of strata near top of geologic column argues for Hesperian age of strata Under 4xLunar ~ 1Billion yrs old

Early Earth and Mars Environments Similar

• Much H2O

• Atmosphere of CO2 H2O and N2

Aqueous Activity but No Carbonates!

CO2 + H2O H2CO3 H2CO3 + (Mg Fe )SiO3 Mg CO3 Fe CO3 + SiO2

CO2 + H2O + O2 H2CO3 + O2 H2CO3 + (Mg Fe )SiO3 Mg CO3 Fe CO3 + SiO2 + O2 MgO + Fe2 O3 + CO2

CO2 + H2O + O2 + SO2 CO2 + H2SO4 H2SO4 + (Mg Fe )SiO3 Mg SO4 Fe 2(SO4 + SiO2 MgO + Fe2 O3 + CO2

Odd Nitrogen in High UV environment

Splitting of water in large amounts by UV should be accompanied by splitting of Nitrogen to form NOx and nitric acid in large amounts

Abiotic Oxygen Production: Photolysis of Water

Oxygen source : UV + 2H2O 2H2 + O2 2H2 rises and is lost Oxygen source : UV + 3O2 2 O3 2H2 rises and is lost H2S + 2O2 H2 SO4 Mg SO4 Fe SO4 + SiO2 H2 SO4 + Mg CO3 Fe CO3 Mg SO4 Fe SO4 + CO2

Should make Nitrates in large amounts! Also, such a process would have operated on Earth and no evidence is seen: Pre-Cambrian sediments have low oxidation state

However, such a process is self-limiting (O2 , O3 are UV absorbers ) and would operate at high altitude and would also produce nitrates in large amounts! via N2 + O2 + UV NOx

Biotic Oxygen Production: Produces O2 with visible light

Oxygen source : Photosynthesis Produces oxidation without nitrates H2S + 2O2 H2 SO4 Mg SO4 Fe SO4 + SiO2 H2 SO4 + Mg CO3 Fe CO3 Mg SO4 Fe SO4 + CO2

Such a process has operated on Earth and produces little nitrate Post Cambrian sediments have high oxidation state , sulfates , and only small amounts of nitrates , matching Mars.

Absence of Nitrates Requires Photosynthesis for High Oxidation

Gale crater Sediments formed in aqueous , highly oxidizing environment This explains lack of carbonates and high abundant ferric iron Where did large quantities of oxygen come from? Two options : Photolysis and Photosynthesis Photolysis would have created nitrates in large amounts, and would have also operated on Earth in the Pre-Cambrian Absence of significant nitrates , and absence of high oxidation until Cambrian on Earth argues for massive photosynthesis when strata formed on Mars

Summary and Conclusions

• The Gale Crater exposed sediments appear to be ~2 Billion years old and were thus formed in the Hesperian or Middle of Mars History

• The exposed strata at Gale crater resembles Post Cambrian Terrestrial aqueous sediments chemically and morphologically

• Nitrates are Absent except for trace amounts

• Sediments argue for Mars bio-stabilized greenhouse during Hesperian