Overview
- A peer-reviewed Science paper led by Timo Hopp reports that Theia most likely originated in the inner Solar System, probably forming closer to the Sun than proto-Earth.
- New high-precision analyses show Earth and Moon iron isotopic compositions are indistinguishable and align with non-carbonaceous meteorites that sample inner Solar System material.
- Reverse-engineering across iron, chromium, molybdenum, and zirconium isotopes indicates Earth and Theia were chemical neighbors during planet formation.
- Mass-balance results portray Theia as a rocky body with a metallic core totaling about five to ten percent of Earth's mass, with excess molybdenum and zirconium in Earth's mantle likely delivered by the impactor.
- The study measured 15 terrestrial rocks, six Apollo lunar samples, and roughly 20 meteorites, and the authors caution that targeted giant-impact simulations and additional lunar samples are still needed.