The origin of the Moon remains one of planetary science's most consequential and incompletely resolved questions. The prevailing Giant Impact Hypothesis, while this model represents current scientific consensus it contains several significant unresolved inconsistencies including problems with conservation of momentum, isotopic similarity between Earth and Moon, the precision of lunar tidal locking, the anomalous longevity and asymmetry of lunar volcanic activity, and the origin of the Large Low Shear Velocity Provinces at Earth's core mantle boundary. This paper proposes an alternative model — the Theia Moon Hypothesis — in which Theia was approximately Moon-sized rather than Mars-sized and executed a grazing collision with early Earth resulting in gravitational capture rather than absorption and debris coalescence. This model proposes that the Moon is substantially the original Theia body, tidally locked instantaneously through collision dynamics, with its near side compositionally and thermally blended with Earth material at the collision interface. The hypothesis generates eight specific testable predictions across lunar science, isotopic geochemistry, deep Earth seismology, thermal geology, orbital mechanics, and planetary formation theory. It provides a novel mechanical explanation for the antipodal placement of the Large Low Shear Velocity Provinces as collision-deposited Theia mantle material — representing independent corroborating evidence from entirely separate scientific disciplines. Trajectory analysis of the LLSVP geometric relationship reveals a near-equatorial collision approach consistent with early solar system ecliptic plane dynamics. The slight deviation of the LLSVPs from perfect antipodality is identified as a predicted signature of grazing rather than direct impact mechanics. This collision geometry additionally predicts Earth's current axial tilt of 23.4 degrees as a direct mechanical consequence — connecting the formation of the Moon, the origin of the LLSVPs, Earth's seasonal obliquity, and the conditions enabling complex life within a single unified collision event preserved in the deep mantle for 4.5 billion years.
Brandon Pyle (Mon,) studied this question.