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

Deng, Jie; Du, Zhuofei; Karki, Bijaya B.; Ghosh, Debashri; Lee, Kanani K. M.

doi:10.1038/s41467-020-15757-0

Cited by 72 publications

(58 citation statements)

References 55 publications

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“…As the example of Venus shows, CO 2 can be an important constituent of atmospheres of rocky planets. CO 2 was also a major constituent of early Earth's atmosphere (e.g., Kasting, 1993;Deng et al, 2020). The amount of CO 2 present in the atmosphere determines whether condensation of water to an ocean can occur.…”

Section: Discussionmentioning

confidence: 99%

Magma Ocean Evolution of the TRAPPIST-1 Planets

et al. 2021

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Recent observations of the potentially habitable planets TRAPPIST-1 e, f, and g suggest that they possess large water mass fractions of possibly several tens of weight percent of water, even though the host star's activity should drive rapid atmospheric escape. These processes can photolyze water, generating free oxygen and possibly desiccating the planet. After the planets formed, their mantles were likely completely molten with volatiles dissolving and exsolving from the melt. To understand these planets and prepare for future observations, the magma ocean phase of these worlds must be understood. To simulate these planets, we have combined existing models of stellar evolution, atmospheric escape, tidal heating, radiogenic heating, magmaocean cooling, planetary radiation, and water-oxygen-iron geochemistry. We present MagmOc, a versatile magma-ocean evolution model, validated against the rocky super-Earth GJ 1132b and early Earth. We simulate the coupled magma-ocean atmospheric evolution of TRAPPIST-1 e, f, and g for a range of tidal and radiogenic heating rates, as well as initial water contents between 1 and 100 Earth oceans. We also reanalyze the structures of these planets and find they have water mass fractions of 0-0.23, 0.01-0.21, and 0.11-0.24 for planets e, f, and g, respectively. Our model does not make a strong prediction about the water and oxygen content of the atmosphere of TRAPPIST-1 e at the time of mantle solidification. In contrast, the model predicts that TRAPPIST-1 f and g would have a thick steam atmosphere with a small amount of oxygen at that stage. For all planets that we investigated, we find that only 3-5% of the initial water will be locked in the mantle after the magma ocean solidified.

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Section: Discussionmentioning

confidence: 99%

Magma Ocean Evolution of the TRAPPIST-1 Planets

et al. 2021

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“…And it is calculated that the core/mantle boundary in Mars is defined by ringwoodite (Mg,Fe) 2 SiO 4 ) to solid iron [ 116 , 117 , 118 ]. In such a case gases evolved from the reduced Martian magmas and resulting from giant impacts would have mainly comprised hydrogen, water vapour, methane and carbon monoxide [ 8 , 16 ]. In fact, notwithstanding earlier arguments [ 119 ], as the olivine/ringwoodite-to-bridgmanite transition is not realized (which requires a pressure of 23 GPa to trigger the said transition), planets the size of Mars or smaller are much less likely to emit large quantities of CO 2 —the staple of life—through degassing and vulcanism [ 16 , 20 , 48 , 116 ].…”

Section: Four Minerals To Set the Stage For Life’s Emergencementioning

confidence: 99%

“…Assuming magma oceans occupied portions of all three planets, it follows that the atmospheres of the early Earth and probably early Venus comprised CO 2 and H 2 O, whereas the early atmosphere/hydrosphere of Mars consisted of H 2 + H 2 O > CH 4 + CO. A percentage of N 2 is common to all [ 98 ]. Figure based on [ 5 , 16 , 20 , 99 , 100 , 101 ].…”

Section: Figurementioning

confidence: 99%

“…A fundamental understanding of what drove life into being on our planet requires knowledge of how inorganic minerals, accreted from the solar disc, responded to physicochemical pressure and stresses induced by convection and differentiation in an early magma ocean [ 7 , 8 , 15 , 16 ]. These dynamic processes provided the ‘bio-elements’ C, H, O, N, P, S, the transition metal sulfide and oxide clusters and both the reductants and oxidants necessary for life’s emergence [ 17 , 18 , 19 , 20 , 21 , 22 ].…”

Section: Introductionmentioning

confidence: 99%

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Six ‘Must-Have’ Minerals for Life’s Emergence: Olivine, Pyrrhotite, Bridgmanite, Serpentine, Fougerite and Mackinawite

Russell

Ponce

2020

Life

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Life cannot emerge on a planet or moon without the appropriate electrochemical disequilibria and the minerals that mediate energy-dissipative processes. Here, it is argued that four minerals, olivine ([Mg>Fe]2SiO4), bridgmanite ([Mg,Fe]SiO3), serpentine ([Mg,Fe,]2-3Si2O5[OH)]4), and pyrrhotite (Fe(1−x)S), are an essential requirement in planetary bodies to produce such disequilibria and, thereby, life. Yet only two minerals, fougerite ([Fe2+6xFe3+6(x−1)O12H2(7−3x)]2+·[(CO2−)·3H2O]2−) and mackinawite (Fe[Ni]S), are vital—comprising precipitate membranes—as initial “free energy” conductors and converters of such disequilibria, i.e., as the initiators of a CO2-reducing metabolism. The fact that wet and rocky bodies in the solar system much smaller than Earth or Venus do not reach the internal pressure (≥23 GPa) requirements in their mantles sufficient for producing bridgmanite and, therefore, are too reduced to stabilize and emit CO2—the staple of life—may explain the apparent absence or negligible concentrations of that gas on these bodies, and thereby serves as a constraint in the search for extraterrestrial life. The astrobiological challenge then is to search for worlds that (i) are large enough to generate internal pressures such as to produce bridgmanite or (ii) boast electron acceptors, including imported CO2, from extraterrestrial sources in their hydrospheres.

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“…Finally, a crucial aspect that determines the chemistry of a secondary atmosphere is the mantle oxidation state. Under reducing conditions, the outgassing of H 2 and CO is favoured, while oxidising conditions favour H 2 O and CO 2 to outgas [21,56]. Changing how reducing an atmosphere is has important implications for prebiotic chemistry [120] and climate [167].…”

Section: Bulk Composition and Consequences For Secondary Atmospheresmentioning

confidence: 99%

Ariel planetary interiors White Paper

et al. 2021

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The recently adopted Ariel ESA mission will measure the atmospheric composition of a large number of exoplanets. This information will then be used to better constrain planetary bulk compositions. While the connection between the composition of a planetary atmosphere and the bulk interior is still being investigated, the combination of the atmospheric composition with the measured mass and radius of exoplanets will push the field of exoplanet characterisation to the next level, and provide new insights of the nature of planets in our galaxy. In this white paper, we outline the ongoing activities of the interior working group of the Ariel mission, and list the desirable theoretical developments as well as the challenges in linking planetary atmospheres, bulk composition and interior structure.

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

Cited by 72 publications

References 55 publications

Magma Ocean Evolution of the TRAPPIST-1 Planets

Magma Ocean Evolution of the TRAPPIST-1 Planets

Six ‘Must-Have’ Minerals for Life’s Emergence: Olivine, Pyrrhotite, Bridgmanite, Serpentine, Fougerite and Mackinawite

Ariel planetary interiors White Paper

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