Thermal Convection in Vesta’s Core from Experimentally-Based Conductive Heat Flow Estimates

Electrical resistivity measurements of Fe-5wt%Ni were made in-situ under pressures of 2-5 GPa and temperatures up to 2000 K in a cubic-anvil press. The thermal conductivity was calculated from the measured electrical resistivity data using the Wiedemann–Franz law. Comparison of these data with previous studies on pure Fe and Fe-10wt%Ni shows that a change in the Ni con-tent within the range 0-10wt% Ni has no significant effect on electrical resistivity of Fe alloys. Comparing the estimated adiabatic core heat flux of ~331 MW at the top of Vesta’s core to the range of estimated heat flux through the CMB of 1.5–78 GW, we infer that the mechanism stir-ring Vesta’s liquid outer core to generate its surface magnetic field tens of millions of years in its early history was thermal convection.本研究采用立方砧压机（cubic-anvil press），在2~5吉帕斯卡（GPa）压力、最高2000开尔文（K）的原位（in-situ）条件下，完成了铁-5重量百分比镍合金（Fe-5wt%Ni）的电阻率测量。本研究通过维德曼-夫兰兹定律（Wiedemann–Franz law），由实测电阻率数据计算得到热导率。将本次实测数据与此前针对纯铁（Fe）以及铁-10重量百分比镍合金（Fe-10wt%Ni）的相关研究进行对比后发现：镍含量在0~10wt%范围内变化时，对铁合金的电阻率无显著影响。将灶神星（Vesta）核顶部约331兆瓦（MW）的估算绝热核热通量，与通过核幔边界（Core-Mantle Boundary，CMB）的1.5~78吉瓦（GW）热通量估算范围进行对比后，我们推断：在灶神星早期数千万年的演化历程中，驱动其液态外核流动以产生地表磁场的机制为热对流（thermal convection）。