Thermal Conductivity of FeS and Its Implications for Mercury's Long‐Sustaining Magnetic Field

Abstract : he MESSENGER mission revealed that Mercury's magneticfield might have operated since3.7–3.9 Ga. While the intrinsic magnetism suggests an active dynamo within Mercury's core, themechanism that is responsible for sustaining the dynamo for prolonged period of time remains unknown.Here we investigated the electrical conductivity of Fe‐S alloys at pressure of 8 GPa and temperatures up to1,700 K. We show that the electrical conductivity of Fe‐S alloys at 1,500 K is about 103S/m, 2 orders ofmagnitude lower than the previously assumed value for dynamo calculations. The thermal conductivity wasestimated using the Wiedemann‐Franz law. The total thermal conductivity of FeS is estimated to be ~4Wm/K at the Mercurian core‐mantle boundary conditions. The low thermal conductivity suggests that athermally driven dynamo operating on Mercury is more likely than expected. If coupled with chemicalbuoyancy sources, it is possible to sustain an intrinsic dynamo during time scales compatible with theMESSENGER observations.
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https://hal.uca.fr/hal-02284266
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Submitted on : Wednesday, September 11, 2019 - 3:54:30 PM
Last modification on : Thursday, September 12, 2019 - 1:19:20 AM

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G. Manthilake, J. Chantel, J. Monteux, D. Andrault, Mohamed Ali Bouhifd, et al.. Thermal Conductivity of FeS and Its Implications for Mercury's Long‐Sustaining Magnetic Field. Journal of Geophysical Research. Planets, Wiley-Blackwell, 2019, ⟨10.1029/2019JE005979⟩. ⟨hal-02284266⟩

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