Energetic Requirements for Dynamos in the Metallic Cores of Super-Earth and Super-Venus Exoplanets

Blaske, Claire; O’Rourke, J. G.

doi:10.1002/essoar.10504701.2

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“…The measured masses and radii of super‐Earths, however, cannot be used to determine a unique solution for their internal structures and core‐mass fractions (CMFs). The possible range of super‐Earth interior density, thermal, and dynamic structures and the effect on their observable properties have been the subject of recent experimental and computational studies (e.g., Blaske & O’Rourke, 2021; Boujibar et al., 2020; Driscoll & Olson, 2011; Dutta et al., 2022; Fei et al., 2021; Tsuchiya & Tsuchiya, 2011; Umemoto et al., 2017).…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Stability of an Eight‐Coordinated Fe₃O₄ High‐Pressure Phase: Implications for the Mantle Structure of Super‐Earths

et al. 2022

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Super‐Earths ranging up to 10 Earth masses (ME) with Earth‐like density are common among the observed exoplanets thus far, but their measured masses and radii do not uniquely elucidate their internal structure. Exploring the phase transitions in the Mg‐silicates that define the mantle‐structure of super‐Earths is critical to characterizing their interiors, yet the relevant terapascal conditions are experimentally challenging for direct structural analysis. Here we investigated the crystal chemistry of Fe3O4 as a low‐pressure analog to Mg2SiO4 between 45–115 GPa and up to 3000 K using powder and single crystal X‐ray diffraction in the laser‐heated diamond anvil cell. Between 60–115 GPa and above 2000 K, Fe3O4 adopts an 8‐fold coordinated Th3P4‐type structure (I‐43d, Z = 4) with disordered Fe2+ and Fe3+ into one metal site. This Fe‐oxide phase is isostructural with that predicted for Mg2SiO4 above 500 GPa in super‐Earth mantles and suggests that Mg2SiO4 can incorporate both ferric and ferrous iron at these conditions. The pressure‐volume behavior observed in this 8‐fold coordinated Fe3O4 indicates a maximum 4% density increase across the 6‐ to 8‐fold coordination transition in the analog Mg‐silicate. Reassessment of the FeO—Fe3O4 fugacity buffer considering the Fe3O4 phase relationships identified in this study reveals that increasing pressure and temperature to 120 GPa and 3000 K in Earth and planetary mantles drives iron toward oxidation.

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Section: Introductionmentioning

confidence: 99%

Synthesis and Stability of an Eight‐Coordinated Fe₃O₄ High‐Pressure Phase: Implications for the Mantle Structure of Super‐Earths

et al. 2022

View full text Add to dashboard Cite

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Energetic Requirements for Dynamos in the Metallic Cores of Super-Earth and Super-Venus Exoplanets

Cited by 1 publication

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Synthesis and Stability of an Eight‐Coordinated Fe₃O₄ High‐Pressure Phase: Implications for the Mantle Structure of Super‐Earths

Synthesis and Stability of an Eight‐Coordinated Fe₃O₄ High‐Pressure Phase: Implications for the Mantle Structure of Super‐Earths

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Energetic Requirements for Dynamos in the Metallic Cores of Super-Earth and Super-Venus Exoplanets

Cited by 1 publication

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Synthesis and Stability of an Eight‐Coordinated Fe3O4 High‐Pressure Phase: Implications for the Mantle Structure of Super‐Earths

Synthesis and Stability of an Eight‐Coordinated Fe3O4 High‐Pressure Phase: Implications for the Mantle Structure of Super‐Earths

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Synthesis and Stability of an Eight‐Coordinated Fe₃O₄ High‐Pressure Phase: Implications for the Mantle Structure of Super‐Earths

Synthesis and Stability of an Eight‐Coordinated Fe₃O₄ High‐Pressure Phase: Implications for the Mantle Structure of Super‐Earths