Effect of Water on the Thermal Properties of Olivine With Implications for Lunar Internal Temperature

Abstract

AbstractHow water could affect thermal transport properties is a key question that needs to be quantified experimentally when it is incorporated as structurally bound hydroxyl groups in the lattice of mantle minerals. In this study, thermal diffusivity (D) and thermal conductivity (κ) of San Carlos olivine aggregates with various water contents (up to 0.2 wt.% H2O) were measured simultaneously using transient plane‐source method up to 873 K and 3 GPa. Experimental results demonstrate that water content can significantly reduce the thermal diffusivity (D) and thermal conductivity (κ) of olivine aggregate. With the increase of H2O content from 0.08 to 0.2 wt.%, the absolute values of D and κ for olivine samples decrease by 5–13% and 17–33% and by 3–8% and 14–21%, respectively. D and κ of olivine aggregate decrease with temperature but increase with pressure. Heat capacity is influenced by pressure negatively. Combining the present data with surface heat flow of the Moon as well as heat production, the calculated temperature profiles provide new constraints on the lunar geotherm and possible H2O content in the lunar interior.