Thermoelastic Properties of Iron-Rich Ringwoodite and the Deep Mantle Aerotherm of Mars

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Wang, Fei ; Bausch, Hannah J. ; Gardner, Laura L. ; Zhang, Dongzhou ; Armstrong, Katherine ; Bell, Aaron S. ; Zhao, Jiyong ; Alp, Ercan E. ; Jacobsen, Steven D.:
Thermoelastic Properties of Iron-Rich Ringwoodite and the Deep Mantle Aerotherm of Mars.
In: Geophysical Research Letters. Bd. 52 (2025) Heft 3 . - e2024GL109666.
ISSN 1944-8007
DOI: https://doi.org/10.1029/2024GL109666

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Abstract

The Martian mantle is considered to have a higher Fe/Mg ratio than the Earth's mantle. Ringwoodite, γ-(Mg,Fe)2SiO4, is likely the dominant polymorph of olivine in the core-mantle boundary (CMB) region of Mars. We synthesized anhydrous iron-rich ringwoodite with molar Mg/(Mg + Fe) = 0.44 and determined its thermal equation of state up to 35 GPa and 750 K by synchrotron X-ray diffraction. Using a third order Birch-Murnaghan equation of state, we obtain KT0 = 182 (3) GPa, K′ = 4.6 (2), and α0 = 3.18 (6) × 10−5 K−1. Using these results and an updated mineralogical model with an iron-rich composition of Mg/(Mg + Fe) = 0.75 for the Martian mantle, we estimate ∼1900 K for the temperature of the D1000 seismic discontinuity inside Mars. The resulting adiabat predicts a warm aerotherm, which could explain the presence of partial melt at the CMB of Mars recently detected with seismic data from the 2019 InSight mission.