Overview
- Earth and the Moon share indistinguishable iron isotopic signatures that align with non‑carbonaceous meteorites thought to represent inner‑Solar‑System material.
- The team measured iron isotopes in 15 terrestrial rocks and six Apollo lunar samples and compared them with meteorites, integrating results with chromium, molybdenum and zirconium data.
- Reverse‑engineering scenarios best fit a Theia that formed in the inner Solar System, likely nearer the Sun than Earth, consistent with Earth and Theia having been close neighbors.
- Theia’s inferred composition does not match known meteorite classes, suggesting a previously unsampled reservoir from the inner Solar System.
- Key uncertainties remain over the degree of impact homogenization and the Moon‑to‑Earth material split, with authors calling for more modeling and new samples; the study appears in Science.