Martian core heat flux: Electrical resistivity and thermal conductivity of liquid Fe at martian core P-T conditions
Martian core heat flux: Electrical resistivity and thermal conductivity of liquid Fe at martian core P-T conditions
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DOI：
10.1016/j.icarus.2021.114367
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发表时间：
2021-03-01
期刊：
影响因子：
3.2
通讯作者：
Yoshino, Takashi
中科院分区：
文献类型：
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作者：
Ezenwa, Innocent C.;Yoshino, Takashi
现在的火星没有磁场，这表明从其液态核心带走的热量主要是由传导驱动的。为了限制来自火星核心的热通量，我们测量了在不同的固定压力（P）下，在大体积压力下，没有污染的固体和液体Fe的温度（T）依赖的电阻率，最高可达22.5 GPa，对应于火星核心顶部的P。我们还测量了它的P相关电阻率高达22.5GPa在室温T。在18和20 GPa之间的P范围内，我们观察到的电阻率下降类似于35 μ Ω厘米，这是由于在长程有序磁结构的损失。这种损失导致由磁振子引起的电子散射过程的总体减少。从长程有序到短程有序的磁性结构的转变与从α-bcc（铁磁性）到ε-hcp（顺磁性）的晶体学转变的完成相关。在相同的P范围内电阻率的降低对应于类似于30 Wm（-1）K-1的热导率的增加。在火星核幔边界（CMB）的液态铁的电阻率和热导率估计为68 +/- 3 μ Ω cm和82 +/- 3 Wm（-1）K-1，分别类似。发现沿其芯层沿着传导的热量近似为45 mW（-1）m（-2）。当核心半径近似为1700 km时，我们得到其总表面热通量的值为0.3 TW。在与铁的电阻率在地球的核心条件下，最近的一项研究报告相比，我们的研究结果表明，纯液态铁是导电的火星核心比在地球的核心。我们的研究结果将补充正在进行的NASA InSight使命中的HP 3地下热通量测量。
The present-day Mars has no magnetic field which suggests that the heat carried out of its liquid core is largely driven by conduction. To constrain the heat flux from Martian core, we measured the temperature (T) dependent electrical resistivity of solid and liquid Fe devoid of contamination in large volume press at various fixed pressure (P) up to 22.5 GPa, corresponding to the P at the top of the Martian core. We also measured its P-dependent resistivity up to 22.5 GPa at room T. At a P range between 18 and 20 GPa, we observed a drop in the electrical resistivity of similar to 35 mu Omega cm which is attributed to a loss in long range order magnetic structure. This loss gives rise to an overall decrease in the electron scattering processes induced by magnon. The transition from long- to short-range order magnetic structure occurs in association with the completion of crystallographic transformation from alpha-bcc (ferromagnetic) to epsilon-hcp (paramagnetic). The decrease in the electrical resistivity at the same P range corresponds to an increase in thermal conductivity of similar to 30 Wm(-1) K-1. The resistivity and thermal conductivity of liquid Fe at the Martian core mantle boundary (CMB) on the cores side are estimated to be similar to 68 +/- 3 mu Omega cm and similar to 82 +/- 3 Wm(-1) K-1, respectively. The heat conducted along its core adiabat is found to be similar to 45 mW(-1) m(-2). With a core radius of similar to 1700 km, we obtain a value of 0.3 TW for its total surface heat flux. In comparison with the resistivity of Fe at the Earth's core conditions reported by a recent study, our result indicates that pure liquid Fe is electrically more conductive in the Martian core than in the Earth's core. Our results will complement the HP3 subsurface heat flux measurements in the on-going NASA InSight Mission.