Mercury's rotation axis and period

Recent measurements made from high-resolution Mariner 10 photography of the planet Mercury yield a rotation period of 58.6461 + or 0.005 days, in excellent agreement with the period required for a precise 2/3 resonance with its orbital period (58.6462 days). The axis of rotation of the planet was calculated to be offset about 2 deg from the perpendicular to its orbital plane within a 50% probability error ellipse of + or - 2.6 deg by + or - 6.5 deg. Dynamical considerations make it most likely that the true displacement from the orbit normal is less than 1 deg.