Electrical resistivity of liquid Fe-8wt%S-4.5wt%Si at high pressures with implications for heat flux through the cores of Io and sub-earth exoplanets

Abstract

Potentially resulting in magnetic dynamo action, the heat flow through the outer cores of small terrestrial planetary bodies depends on the thermal conductivity of liquid Fe alloys at high pressures. The electrical resistivity of liquid Fe-8wt%S-4.5wt%Si was measured at 2–5 GPa and 295–1800 K in a 1000-ton cubic anvil press with a sample volume of a few cubic millimeters. Resistivity values of 220–270 μΩ·cm were measured, and a range of thermal conductivity values of 15–19 W/m/K were calculated using the Wiedemann-Franz law. The adiabatic heat flux at the top of a terrestrial exoplanet's Fe-8wt%S-4.5wt%Si core as a function of radius is calculated. The core of Io, if liquid, could have a convective heat flow density of a few μW/m2 without generating a magnetic dynamo powered by thermal convection.