Constraining the structure and composition of the Moon-forming impactor and the proto-Earth
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The Moon-forming giant impact, involving a collision between the proto-Earth and a planetary body known as Theia, presents considerable challenges, particularly regarding Theia's and proto-Earth’s characteristics. By integrating impact numerical modelling with data from meteorites, we can bring further constraints on their mantle composition and Theia's core mass fraction (CMF). Our findings indicate that Theia's CMF is below 35%. Moreover, Theia’s mantle is composed of differentiated materials similar to Aubrites, whereas the proto-Earth’s mantle exhibits a composition akin to that of the presented-day Earth. After the impact, parts of Theia's mantle were incorporated into the proto-Earth, while the proto-Earth’s composition remained largely unaltered. Other portions of Theia either participated in the formation of the Moon or escaped the Earth-Moon system. Our research provides a quantitative constraint on Theia and proto-Earth and demonstrates their similarities, mitigating the isotope crisis in the Earth-Moon system and offering a pathway to probe Theia's mantle material.
