Saturn's atmospheric temperature structure and heat budget

The effective temperature of Saturn from 30°S to 10°N is 96.5 ± 2.5 K. This value is 1.9 K higher than our preliminary estimate (Ingersoll et al., 1980). The atmospheric mole fraction of H_2 relative to H_2 + He is 90 ± 3%. This value is derived by comparing infrared and radio occultation data (Kliore et al., this issue) for the same latitude. The high value of the effective temperature suggests that Saturn has an additional energy source besides cooling and contraction. The high mole fraction of H_2 suggests that separation of heavier He toward the core may be supplying the additional energy. Atmospheric temperatures in the 60- to 600-mbar range are 2.5 K lower within 7° of the equator than at higher latitudes. An almost isothermal layer exists between 60 and 160 mbar at all latitudes