Explaining Mercury's Density through Magnetic Erosion

TL;DR

This paper proposes magnetic erosion in protoplanetary disks as a process that can explain Mercury's large iron core by selectively removing silicate material from iron-rich dust grains during planet formation.

Contribution

It introduces the concept of magnetic erosion as a novel mechanism influencing planetary core composition, specifically explaining Mercury's density.

Findings

Magnetic erosion can lead to iron-enriched planetesimals.

This process may account for Mercury's disproportionately large iron core.

Abstract

In protoplanetary disks, dust grains rich in metallic iron can attract each other magnetically. If they are magnetized to values near saturation, the magnetically induced collision speeds are high enough to knock off the non-magnetized, loosely bound silicates. This process enriches the surviving portions of the dust grains in metallic iron, which further enhances the magnetically mediated collisions. The magnetic enhancement to the collisional cross-section between the iron rich dust results in rapid grain growth leading to planetesimal formation. While this process of knocking off silicates, which we term "magnetic erosion", occurs only in a very limited portion of a protoplanetary disk, it is a possible explanation for Mercury's disproportionately large iron core.