The rotation of the planet Mercury

Radar observations of Mercury have disclosed that the sidereal period of the planet's axial rotation is 59 + 3 days (Pettengill and Dyce, 1965; Dyce et al., 1966), rather than the previously accepted period of 88 days (see, for example, Dollfus, 1953). The purpose of our investigation is to discover the implications for our theories of the solar system (and of the inner planets in particular) which this new result may require.