Redox Processes Before, During, and After Earth's Accretion Affecting the Deep Carbon Cycle

Stagno, Vincenzo; Aulbach, Sonja

doi:10.1002/9781119473206.ch2

Cited by 11 publications

(9 citation statements)

References 98 publications

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“…Achieving higher values of (Fe 3+ /FeT)bg of 0.50 would require initial bulk (Fe 3+ /FeT) up to or greater than 0.50, which would predict final outgassed atmospheres with fO2 = IW+7 -IW+9, well above present day upper mantle oxidation state (QFM ~IW+4) and high enough that molecular O2 gas would be significant in the outgassed atmosphere. We find this an implausible result, given evidence that the Archean mantle was 1 to 2 log units more reduced than the present day (Aulbach & Stagno 2016, Nicklas et al 2019, Gao et al 2022, Stagno & Aulbach 2021.…”

Section: Bridgmanitementioning

confidence: 66%

Ferric iron evolution during crystallization of the Earth and Mars

Schaefer,

Pahlevan,

Elkins-Tanton

2024

Preprint

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Magma ocean crystallization models that track fO2 evolution can reproduce the D/H ratios of both the Earth and Mars without the need for exogenous processes. Fractional crystallization leads to compositional evolution of the bulk oxide components. Metal-saturated magma oceans have long been thought to contain negligible ferric iron oxide (Fe3+O1.5), but recent work suggests they may contain near-present-day Fe3+ concentrations. We model the fractional crystallization of Earth and Mars, including Fe2+ and Fe3+ as separate components. We use two independent equations of state (Deng, Armstrong EOS) to calculate Fe3+ partition coefficients for lower mantle minerals and compare results of fractional crystallization for different magma ocean configurations for both Earth and Mars. We calculate the oxygen fugacity (fO2) at the surface as the systems evolve and compare them to constraints on the fO2 of the last magma ocean atmosphere from D/H ratios. For Earth, we find that Fe3+ must behave incompatibly in the lower mantle to match the D/H constraint for whole mantle models, but shallow magma ocean models also provide reasonable matches to the constraints. For Mars, both EOSs produce near identical results but cannot match the D/H constraints on last fO2 unless the magma ocean begins with less than 50% of the predicted Fe3+. This model shows that Fe3+ partitioning has a measurable effect on magma ocean atmosphere redox state, which is not a static quantity but evolves throughout the magma ocean’s lifetime. We highlight the need for additional experimental constraints on ferric iron partitioning.

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Section: Bridgmanitementioning

confidence: 66%

Ferric iron evolution during crystallization of the Earth and Mars

Schaefer,

Pahlevan,

Elkins-Tanton

2024

Preprint

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“…This interpretation is consistent with the reported thermodynamic stability of manganese and iron oxides, carbonates and disulphides at kiln temperatures (900–1100 °C). 37,38 Note that whilst the kiln temperature is controlled to avoid sintering (dead-burned lime), the maximum upper temperature is close to that for the tetragonal-to-cubic phase change of the hausmannite spinel (1170 °C). 39…”

Section: Manganese and Iron Impurities In Slaked Limesmentioning

confidence: 99%

Empowering clean water whilst safeguarding water distribution pipeline integrity: towards manganese- and iron-free lime hydrate for water treatment

Wadhawan

Kocsis

Meyer

et al. 2023

Environ. Sci.: Water Res. Technol.

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“…Thus, from a chemical point of view, the prebiotic Earth should have been a very different world than the one we inhabit today. As a result of Earth's lithosphere and crust composition being close to the quartz-fayalite-magnetite mineral buffer (Stagno & Aulbach 2021), modern volcanic emissions are dominated by oxidized gases, such as H 2 O and CO 2 . However, geochemical analyses of Archean and Hadean rock samples (Trail et al 2012;Rollinson et al 2017) suggest similar conditions on the earliest Earth, potentially the result of disproportionate ferrous and ferric iron in the mantle (Armstrong et al 2019;Hirschmann 2022), as well as hydrogen loss from the early atmosphere (Lammer et al 2018;Yoshida & Kuramoto 2021).…”

Section: Introductionmentioning

confidence: 99%

Reduced Late Bombardment on Rocky Exoplanets around M Dwarfs

Lichtenberg

Clement

2022

ApJL

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Ocean-vaporizing impacts of chemically reduced planetesimals onto the early Earth have been suggested to catalyze atmospheric production of reduced nitrogen compounds and trigger prebiotic synthesis despite an oxidized lithosphere. While geochemical evidence supports a dry, highly reduced late veneer on Earth, the composition of late-impacting debris around lower-mass stars is subject to variable volatile loss as a result of their hosts’ extended pre-main-sequence phase. We perform simulations of late-stage planet formation across the M-dwarf mass spectrum to derive upper limits on reducing bombardment epochs in Hadean-analog environments. We contrast the solar system scenario with varying initial volatile distributions due to extended primordial runaway greenhouse phases on protoplanets and the desiccation of smaller planetesimals by internal radiogenic heating. We find a decreasing rate of late-accreting reducing impacts with decreasing stellar mass. Young planets around stars ≤0.4 M ⊙ experience no impacts of sufficient mass to generate prebiotically relevant concentrations of reduced atmospheric compounds once their stars have reached the main sequence. For M-dwarf planets to not exceed Earth-like concentrations of volatiles, both planetesimals, and larger protoplanets must undergo extensive devolatilization processes and can typically emerge from long-lived magma ocean phases with sufficient atmophile content to outgas secondary atmospheres. Our results suggest that transiently reducing surface conditions on young rocky exoplanets are favored around FGK stellar types relative to M dwarfs.

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Redox Processes Before, During, and After Earth's Accretion Affecting the Deep Carbon Cycle

Cited by 11 publications

References 98 publications

Ferric iron evolution during crystallization of the Earth and Mars

Ferric iron evolution during crystallization of the Earth and Mars

Empowering clean water whilst safeguarding water distribution pipeline integrity: towards manganese- and iron-free lime hydrate for water treatment

Reduced Late Bombardment on Rocky Exoplanets around M Dwarfs

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