Mercury: Infrared Evidence for Nonsynchronous Rotation

See allHide authors and affiliations

Science  02 Sep 1966:
Vol. 153, Issue 3740, pp. 1112-1113
DOI: 10.1126/science.153.3740.1112


An infrared observation of the dark side of Mercury made by Pettit and Nicholson in 1923 led them to suggest that the planet rotates nonsynchronously. Their early measurements, if taken at face value, would imply a brightness temperature of about 180°K for the dark side. The asymmetry of the infrared phase curve is further interpreted as suggesting direct rotation.