Planetary Composition from Gravitational Position on a Three-Phase Wave

A planet's surface gravity, combined with the three-phase geometry of a Z₃ strip, determines which elements are stable, which harmonic families are present, and what the local coupling constants are. The exact identity sin(60°+δ) − sin(60°−δ) = sin(δ) proves gravity equals the EM–Weak asymmetry: one gravity measurement fixes all three mode amplitudes. Applied to the solar system, Mercury/Venus/Earth cluster at δ ≈ 2° with nearly identical coupling constants, while Mars and the Moon sit closer to the anti-gravity node with weaker binding. Iron fraction follows 0.25/orbit^1.04. Every major rock-forming element is a DST interval from oxygen. Titan's nitrogen atmosphere and Pluto's methane ice match the framework's prediction that light harmonics dominate at large orbital distances. A precision atomic clock on Mars should show coupling constant differences beyond general relativistic predictions.