Electrical Conductivity of Almandine‐Rich Garnet at High Pressures and Temperatures: Constrains on the Conductivity Profile of the Moon and Mars

Abstract Despite the existence of several geophysical models for Mars and the Moon, the composition and structure of their mantles require further constraints; thus, the elastic and electrical properties of relevant minerals and rocks are essential for interpreting those models and elucidating the composition and redox state of these planetary interiors. In this study, we performed electrical conductivity measurements on almandine‐rich garnet at 4–10 GPa and 773–1,523 K using impedance spectroscopy. The results indicate a strong temperature dependence but only a minor pressure dependence. Two conduction mechanisms were identified: small polaron hopping, with an activation energy of 70.65 kJ/mol and an activation volume of −1.02 cm 3 /mol, and ionic conduction, characterized by an activation energy of 140.90 kJ/mol and an activation volume of 0.16 cm 3 /mol. By combining our measurements with modal geotherms, iron contents, and oxygen fugacity () conditions appropriate for the Moon and Mars, we derived bulk electrical conductivities in the ranges 10 −4.3 –10 −1.0 S/m for the lunar mantle and 10 −3.5 –10 −0.2 S/m for the Martian mantle, respectively.