Resonant Rotation for Venus?

Abstract

CAN the rotation period of Venus be commensurate with its synodic period? If the rotation period is 243.16 days retrograde, the axis of Venus which points toward the Earth at one inferior conjunction will point toward the Earth at all subsequent inferior conjunctions. This value for the rotation period of Venus lies within the errors of the measured rotation period^1–3. If the moment of inertia of Venus about this axis is minimal, it is possible that the planet is locked into this synodic commensurability with its permanent bulge or longest axis pointed toward the Earth at each inferior conjunction. In other words, the presence of the Earth may have stabilized the sidereal rotation period of Venus at the value of 243.16 days retrograde. To investigate the stability of such a commensurate spin angular velocity for Venus, we shall use a method similar to that used to determine the stability of the spin angular velocities of Mercury which are commensurate with its orbital angular velocity⁴.