The transport properties of planetary core materials dominate heat transfer through thermal convection, which is closely linked to the geodynamo of the planetary core. Light elements S and P in the lunar core can significantly affect the electrical resistivity and thermal conductivity of lunar core.
Researchers from the Institute of Geochemistry of the Chinese Academy of Sciences (IGCAS) used the van-der Pauw method to measure the electrical resistivity of Fe-S-P alloys under lunar core relevant conditions to investigate the thermal and dynamo evolution of the lunar core.
Figure 1: Resistivity measurement results of different iron alloys.Image by IGCAS）
They estimated the thermal conductivity at the lunar core-mantle boundary using the Wiedemann-Franz law, as 23.34-24.03 W/m/K, based on the measured electrical resistivity of Fe-S-P alloys. The adiabatic heat flux was calculated as 2.06-2.34 mW/m2, while the adiabatic heat flow was about 2.82-3.20 GW.
Furthermore, the researchers modeled the growth of the lunar solid core and demonstrated that the inner core nucleated at 4.35 Ga and the solidification regime switched at 3.50 Ga. The adiabatic heat conduction at the lunar core-mantle boundary indicated that a thermally driven dynamo persisted until 3.78-3.51 Ga in the Moon's history. They also discussed the cessation of the lunar core dynamo in relation to the buoyancy flux, entropy, Reynolds number and Elsasser number and explained the variation in the magnetic field in conjunction with the previous dynamo mechanism.
The study was published in Geophysical Research Letters on July 28.
"These findings provide a profound insight of the Thermal and Dynamo Evolution of the Fe-S-P Lunar Core" according to Prof. Zhai.Shuangmeng.
Contact:
Dr. YIN Yuan、Dr.ZHAI Shuangmeng,
Institute of Geochemistry, Chinese Academy of Sciences
Email: yinyuan@mail.gyig.ac.cn; zhaishuangmeng@mail.gyig.ac.cn
(By Prof. ZHAI shuangmeng' s Group)
