The Composite Infrared Spectrometer (CIRS) consists of two interferometers, one polarizing, the other a conventional Michaelson interferometer, which together provide broad spectral coverage from 10 cm-1 to 1400 cm-1 (1 mm to 7 μ m), at a resolution as high as 0.5 cm-1. CIRS functions both as a thermometer and assayer of the target body, retrieving both thermal structure and composition. The Cassini spacecraft's 140-RJ flyby past Jupiter has enabled CIRS to observe Jupiter, its satellites, and its ring for six months with a spatial resolution up to 2.5o of jovian latitude at the subspacecraft point. This talk will include early results on Jupiter's atmospheric composition obtained from the relatively unexplored spectral region >50 μm, Jupiter's planetary-scale temperature field, and the compositional anomalies and temperatures associated with its auroral hot spots.
view Abstract Citations (78) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Effect of Radiative Transport on the Evolution of Jupiter and Saturn Guillot, T. ; Chabrier, G. ; Gautier, D. ; Morel, P. Abstract Conventional evolutionary models for Jupiter and Saturn, which assume convection throughout the entire planet interior, yield ages of 5.1 Gyr for Jupiter and 2.6 Gyr for Saturn. Even though the discrepancy for Saturn can be explained by the additional energy source due to a phase separation of helium, it seems difficult to reconcile the age of fully convective Jovian models with the age of the solar system, i.e., 4.5 Gyr. It has been recently shown that these planets are probably not fully convective, but retain a stable radiative window near the surface. We present new evolutionary models for these two planets, which do include the aforementioned possibility of radiative transport in the molecular hydrogen-helium envelope. These calculations yield ages of 4.2 Gyr for Jupiter and 2.4 Gyr for Saturn. We show that the importance of the radiative window was larger in the past than now, so that the ratio of the radiative to the adiabatic gradient in the radiative region increases with time. This speeds up the cooling with respect to a fully adiabatic planet. Since the interiors of the new Jupiter and Saturn models are significantly cooler than the adiabatic ones, it is likely that immiscibility of helium occurs in both planets. That provides a natural explanation for the observed helium depletion in their atmospheres and the fact that the ages inferred from homogeneous evolution models of these two planets are smaller than the age of the solar system. Publication: The Astrophysical Journal Pub Date: September 1995 DOI: 10.1086/176156 Bibcode: 1995ApJ...450..463G Keywords: CONVECTION; PLANETS AND SATELLITES: INDIVIDUAL JUPITER; PLANETS AND SATELLITES: INDIVIDUAL SATURN; RADIATIVE TRANSFER full text sources ADS |
The identification of the Jovian frequency spectrum obtained by Schmider et al. (1990, 1991) is proposed, from Doppler shift observations of the solar sodium D line reflected by the planet, as a signature of Jovian global pressure modes. This spectrum, derived from 4 nights of observations, presents high-amplitude peaks whose origin is undoubtedly not noise, but it suffers from the daily interruption in the observations. Echelle diagram analysis has allowed the determination of a regular pattern, corresponding to the regularity indicatged by the asymptotic theory revised for Jovian seismology
There are currently two classes of theories of formation of giant planets: the nucleation model and the gas instability model. The comparison of atmospheric compositions of giant planets permits a test of these. The observed enhancement in CNO compounds in all giant planets, and in deuterium in Uranus, compared with the solar abundance, is consistent with the nucleation model in which a core first grows from accretion of planetesimals and subsequently attracts the surrounding gaseous material of the nebula. However, available data do not permit us to definitively exclude the gas instability model. The agreement of the helium abundance observed in Uranus with the solar value and the depletion observed in Jupiter and Saturn is well explained by the differentiation of helium from metallic hydrogen occurring in the interiors of Jupiter and Saturn but not within Uranus where hydrogen cannot become metallic. Accurate in situ measurements of elemental and isotopic ratios made aboard atmospheric probes descending into atmospheres of giant planets are indispensable for a firm discrimination between various theories of planetary formation.
