Electrical and Thermal Conductivity of Earth's Iron-enriched Basal Magma Ocean

TL;DR

This study uses ab-initio simulations to explore how iron enrichment influences the electrical and thermal conductivities of Earth's basal magma ocean, shedding light on its potential to sustain a magnetic dynamo over geological timescales.

Contribution

It provides new insights into the effects of iron content on the electrical and thermal properties of the basal magma ocean using first-principles calculations.

Findings

Electrical conductivity exceeds 10,000 S/m at relevant conditions.

Iron enrichment significantly affects the thermal conductivity.

Results suggest conditions conducive to dynamo activity over Earth's history.

Abstract

The Earth's earliest magnetic field may have originated in a basal magma ocean, a layer of silicate melt surround the core that could have persisted for billions of years. Recent studies show that the electrical conductivity of liquid with a bulk silicate Earth composition exceeds 10000 S/m at basal magma ocean conditions, potentially surprising the threshold for dynamo activity. Over most of its history however, the basal magma ocean is more enriched in iron than the bulk silicate Earth, due to iron's incompatibility in the mineral assemblages of the lower mantle. Using ab-initio molecular dynamics calculations, we examine how iron content affects the silicate dynamo hypothesis. We investigate how the electrical conductivity of silicate liquid changes with iron enrichment, at pressures and temperatures relevant for Earth's basal magma ocean. We also compute the electronic contribution to the thermal conductivity , to evaluate convective instability of basal magma oceans. Finally, we apply our results to model the thermal and magnetic evolution of Earth's basal magma ocean over time.