Deep magma ocean formation set the oxidation state of Earth’s mantle

Armstrong, Katherine; Frost, Daniel J.; McCammon, Catherine; Rubie, D. C.; Ballaran, Tiziana Boffa

doi:10.1126/science.aax8376

Cited by 141 publications

(131 citation statements)

References 69 publications

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“…The success of core formation and an oxidized atmosphere setting (S/N) OE , (C/N) OE , and (C/S) OE ratios given a gas-poor bulk Earth ( Figure 6) is consistent with the recent predictions of magma ocean ƒO 2 profiles with depth 40,41 , where deep magma oceans are expected to co-exist with oxidized atmospheres.…”

Section: Modeling Observable N-s-c Ratios Of Planets In Response To Psupporting

confidence: 85%

“…If it is, then this model is identified as successful and conditions are logged (Figure 4d-f). the pressure-dependence of Fe +3 -Fe +2 equilibria 40,41 . Satisfying (C/S) OE ratios, on the other hand, requires oxidizing atmospheric conditions.…”

Section: Modeling Observable N-s-c Ratios Of Planets In Response To Pmentioning

confidence: 99%

“…We then calculate bulk Earth nitrogen and carbon contents as a function of sulfur content using the S/N and C/N ratios from different groups of chondrites7 .For each core formation pressure evaluated, we also explore the effect of atmospheric ƒO 2 (IW+4 to IW-3) as an independent variable(Figure 4a-c). Variations in atmospheric state may be driven by changes in ferric iron stability with pressure40,41 and can lead to more reducing or more oxidizing shallow conditions compared to that associated with metal-magma reactions at depth. Atmosphere ƒO 2is important for N and C because their volatility also depends on their dominant valance state.…”

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confidence: 99%

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Core formation and magma ocean outgassing set planetary N-S-C ratios

Jackson

Cottrell

et al. 2020

Preprint

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Earth’s volatile elements cannot be accounted for as mixtures of different chondrites, despite their clear chondritic heritage. Early-acting, but as yet unidentified, processes apparently fractionated volatile elements now contained by planets. Here we test the hypothesis that planetary-scale differentiation, namely core formation and primordial atmosphere degassing, set Earth’s distribution of N, S, and C. To this end, we report new metal-silicate partitioning experiments on N up to 26 GPa and 3400 K; the highest pressure and temperatures conditions yet explored. Our results highlight a strong, positive effect of pressure on nitrogen partitioning into cores. We apply our new experiments with literature data for S and C partitioning to a model that couples core formation with degassing into the primordial atmosphere, to demonstrate that volatile elements ratios for Earth, and potentially Mars and Venus, can be set by primordial differentiation under conditions that also satisfy their moderately siderophile element budgets.

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Section: Modeling Observable N-s-c Ratios Of Planets In Response To Psupporting

confidence: 85%

Section: Modeling Observable N-s-c Ratios Of Planets In Response To Pmentioning

confidence: 99%

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Core formation and magma ocean outgassing set planetary N-S-C ratios

Jackson

Cottrell

et al. 2020

Preprint

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“…Thus, carbon and nitrogen were supplied in graphite and nitrides. Therefore, the Hadean atmosphere and mantle were probably initially highly reducing, before subsequent oxidation either by hydrogen escape (29) or disproportionation of mantle FeO accompanied by Fe loss to the core (30,31). In any case, iron-cored impactors would reduce seawater to hydrogen and create transient, highly reducing atmospheres that may have been important for the origin of life (32,33).…”

Section: A Brief Overview Of the Environment Before The Archeanmentioning

confidence: 99%

The Archean atmosphere

2020

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The atmosphere of the Archean eon—one-third of Earth’s history—is important for understanding the evolution of our planet and Earth-like exoplanets. New geological proxies combined with models constrain atmospheric composition. They imply surface O2 levels <10−6 times present, N2 levels that were similar to today or possibly a few times lower, and CO2 and CH4 levels ranging ~10 to 2500 and 102 to 104 times modern amounts, respectively. The greenhouse gas concentrations were sufficient to offset a fainter Sun. Climate moderation by the carbon cycle suggests average surface temperatures between 0° and 40°C, consistent with occasional glaciations. Isotopic mass fractionation of atmospheric xenon through the Archean until atmospheric oxygenation is best explained by drag of xenon ions by hydrogen escaping rapidly into space. These data imply that substantial loss of hydrogen oxidized the Earth. Despite these advances, detailed understanding of the coevolving solid Earth, biosphere, and atmosphere remains elusive, however.

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“…These contrasting oxidization states may have been set up during the early phase of planetary formation when magma oceans (MOs) could have existed 3,12 . Such an MO involved mechanism has yet to be fully established because relevant redox controlling reactions are still poorly constrained in realistic magma ocean scenarios.…”

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A magma ocean origin to divergent redox evolutions of rocky planetary bodies and early atmospheres

Deng

Karki

et al. 2020

Nat Commun

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Magma oceans were once ubiquitous in the early solar system, setting up the initial conditions for different evolutionary paths of planetary bodies. In particular, the redox conditions of magma oceans may have profound influence on the redox state of subsequently formed mantles and the overlying atmospheres. The relevant redox buffering reactions, however, remain poorly constrained. Using first-principles simulations combined with thermodynamic modeling, we show that magma oceans of Earth, Mars, and the Moon are likely characterized with a vertical gradient in oxygen fugacity with deeper magma oceans invoking more oxidizing surface conditions. This redox zonation may be the major cause for the Earth's upper mantle being more oxidized than Mars' and the Moon's. These contrasting redox profiles also suggest that Earth's early atmosphere was dominated by CO 2 and H 2 O, in contrast to those enriched in H 2 O and H 2 for Mars, and H 2 and CO for the Moon.

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Deep magma ocean formation set the oxidation state of Earth’s mantle

Cited by 141 publications

References 69 publications

Core formation and magma ocean outgassing set planetary N-S-C ratios

Core formation and magma ocean outgassing set planetary N-S-C ratios

The Archean atmosphere

A magma ocean origin to divergent redox evolutions of rocky planetary bodies and early atmospheres

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