Lunar Origin from the Jovian Disruption of Tiamat: A Unified Model for the Earth-Moon System, Venus, the Asteroid Belt, and the Galilean Satellites

The canonical giant impact hypothesis requires the impactor Theia to have formed at the same heliocentric distance as Earth to explain the oxygen and chromium isotopic identity between Earth and Moon — an unsubstantiated coincidence. Here we propose that the Moon formed from a large mantle fragment of Tiamat, a ~0.5 Earth-mass differentiated embryo that accreted at 2–3 au and was tidally disrupted by Jupiter during the Grand Tack migration. N-body simulations (>5000 test particles, 13 configurations) show that Earth-crossing efficiency depends on Jupiter's position: 0.58% at 5.2 au, rising 60-fold to 31.25% at 2.0 au with Saturn. Angular momentum analysis of 466 Earth-crossing fragments yields a predicted obliquity of 0.77°, far below Earth's 23.44°, requiring a final large impactor — Theia — whose isotopic identity with Earth is guaranteed by their common origin. The model simultaneously explains nine independent observations. Six falsifiable predictions are presented.