Work

Martian differentiation history inferred from copper isotopes

Year: 2025

Type: article

Abstract: Sulfide segregation plays an important role in redistributing chalcophile elements during planetary differentiation, yet its efficiency on Mars remains poorly constrained. Here, we report the Cu isotopic evidence for planetary-scale sulfide segregation during martian differentiation. We find that the bulk silicate Mars exhibits a measurable enrichment in isotopically heavy Cu (δ65CuBSMa = −0.03 ± 0.08‰, 2 SD) compared with its chondritic precursors (δ65Cu = −0.30 ± 0.09‰). This isotopic offset cannot be explained by magma ocean devolatilization alone and instead requires preferential incorporation of isotopically light Cu into the core via sulfide segregation. A two-stage core formation model, constrained by established martian building blocks, yields an upper limit for mantle sulfur (400–443 μg/g) with corresponding copper (6–8 μg/g) abundances. These values are consistent with previous estimates for a sulfur-poor martian mantle, as such a mantle facilitates the generation of S-undersaturated melts. Our model further supports a sulfur-rich martian core (~16.1 wt.% S and ~354 μg/g Cu). These findings identify sulfide segregation as a key control on Cu isotopic compositions and chalcophile element budgets during planetary differentiation, providing constraints on Mars’ early evolution. Copper isotopes in the martian mantle are heavier than those in chondritic precursors, indicating that sulfides extracted isotopically light copper into the core during planetary differentiation. This process resulted in a sulfur-poor mantle and a sulfur-rich core, accounting for the observed depletion of chalcophile elements in the mantle. Isotopic evidence and modeling further reveal the history of martian differentiation, providing new insights into the early evolution of Mars.

Source: Nature Communications

DOI: 10.1038/s41467-025-64331-z