The thermal structure of Jupiter I. Implications of Pioneer 10 infrared radiometer data

Temperature profiles for low latitude regions of Jupiter in the 1.0-0.1 bar pressure regime are recovered from Pioneer 10 infrared radiometer data. The temperature near 0.1 bar is 108–117K, depending on the overlying thermal structure assumed. For the South Equatorial Belt, the temperature at 1.0 bar is 170 K, assuming an adiabatic lapse rate in the deep atmosphere. The South Tropical Zone temperature at this level is 155K if pure gaseous absorption is assumed. Alternatively, the temperature is much closer to that in the SEB, assuming the presence of an optically opaque cloud near the 0.6atm (145K) level. Such a cloud presence in the STrZ may be correlated with the visible and 5 micron appearance of the planet and with NH₃ saturation just below this position. The molar fraction of H₂ most consistent with the data is 0.91 ± 0.08. conditional on the perfect validity of the model and the lack of systematic errors in the data. The effective temperatures of the SEB and STrZ are 127.6 and 124.2K, respectively. These temperature profiles are generally consistent with data at other wavelengths and radiative-equilibrium models, but a discrepancy with the preliminary neutral atmosphere inversion of Pioneer 10 radio occultation data remains unexplained.