A New Hypothesis for the Non-equilibrium Figure of the Moon

Abstract

THE deviation of the lunar figure from hydrostatic form may impose theoretical limitations on the thermal state of the interior. This deviation is indicated, not by the geometrical form, but by the ellipsoid of inertia, and the triaxiality of this ellipsoid is several times greater than can be explained by the rotation plus the tidal influence of the Earth. According to Jeffreys¹: (C−A)/C = 0.0006269 ± 27, (B−A)/C = 0.000118 ± 57 Although the equatorial ellipticity is far smaller than the general flattening, which is the main feature, some authors continue to suppose that the Moon possesses solidified tidal bulges associated with a former closer distance to the Earth. But then (C−A)/(B–A) would necessarily be 4/3. In view of the fact that (B−A)/C can be determined with only poor precision, it was long supposed that further observations would lead to better agreement with the hypothesis of a solidified tide, but the latest degree of precision now excludes this hope.