  By analogy with a mechanism proposed by Gold and Soter to explain the
retrograde rotation of Venus, Arras and Socrates suggest that thermal tides may
excite hot jovian exoplanets into nonsynchronous rotation, and perhaps also
noncircular orbits. It is shown here that because of the absence of a solid
surface above the convective core of a jovian planet, the coupling of the
gravitational and thermal tides vanishes to zeroth order in the ratio of the
atmospheric scale height to the planetary radius. At the next order, the effect
probably has the sign opposite to that claimed by the latter authors, hence
reinforcing synchronous and circular orbits.
