The planets: Peter Francis: Penguin Books, 1981, 411pp. U.K. £3.95

Abstract

I compute speed of sound profiles for the four giant planets using simple atmosphere models, and explore the effect on the profiles of ortho : para hydrogen conversion, and the drop in mixing ratio of condensible species at the tropopause. The speed of sound is in general somewhat lower (principally due to lower temperature and higher relative molecular mass) in Uranus and Neptune than in Saturn and Jupiter. Furthermore, the two outer planets show dramatic (∼10%) changes in sound speed due to the condensation of methane, suggesting that sound speed measurement on a probe is a useful diagnostic of vertical structure. Sound Speed measurements for Jupiter and Saturn need to be made with much higher accuracy (∼0.02% for Jupiter and 0.1% for Saturn) to usefully constrain structure and transport. Some instrumental considerations are discussed.