共查询到20条相似文献，搜索用时 218 毫秒
1.
Infrared spectral observations of Mars, Jupiter, and Saturn were made from 100 to 470 cm?1 using NASA's G. P. Kuiper Airborne Observatory. Taking Mars as a calibration source, we determined brightness temperatures of Jupiter and Saturn with approximately 5 cm?1 resolution. The data are used to determine the internal luminosities of the giant planets, for which more than 75% of the thermally emitted power is estimated to be in the measured bandpass: for Jupiter LJ = (8.0 ± 2.0) × 10?10L⊙ and for Saturn LS = (3.6 ± 0.9) × 10?10. The ratio R of thermally emitted power to solar power absorbed was estimated to be RJ = 1.6 ± 0.2, and RS = 2.7 ± 0.8 from the observations when both planets were near perihelion. The Jupiter spectrum clearly shows the presence of the rotational ammonia transitions which strongly influence the opacity at frequencies ?250 cm?1. Comparison of the data with spectra predicted from current models of Jupiter and Saturn permits inferences regarding the structure of the planetary atmospheres below the temperature inversion. In particular, an opacity source in addition to gaseous hydrogen and ammonia, such as ammonia ice crystals as suggested by Orton, may be necessary to explain the observed Jupiter spectrum in the vicinity of 250 cm?1. 相似文献
2.
S K Atreya M H Wong T C Owen P R Mahaffy H B Niemann I de Pater P Drossart T h Encrenaz 《Planetary and Space Science》1999,47(10-11):1243-1262
We present our current understanding of the composition, vertical mixing, cloud structure and the origin of the atmospheres of Jupiter and Saturn. Available observations point to a much more vigorous vertical mixing in Saturn's middle-upper atmosphere than in Jupiter's. The nearly cloud-free nature of the Galileo probe entry site, a 5-micron hotspot, is consistent with the depletion of condensable volatiles to great depths, which is attributed to local meteorology. Somewhat similar depletion of water may be present in the 5-micron bright regions of Saturn also. The supersolar abundances of heavy elements, particularly C and S in Jupiter's atmosphere and C in Saturn's, as well as the progressive increase of C from Jupiter to Saturn and beyond, tend to support the icy planetesimal model of the formation of the giant planets and their atmospheres. However, much work remains to be done, especially in the area of laboratory studies, including identification of possible new microwave absorbers, and modelling, in order to resolve the controversy surrounding the large discrepancy between Jupiter's global ammonia abundance, hence the nitrogen elemental ratio, derived from the earth-based microwave observations and that inferred from the analysis of the Galileo probe-orbiter radio attenuation data for the hotspot. We look forward to the observations from Cassini-Huygens spacecraft which are expected to result not only in a rich harvest of information for Saturn, but a better understanding of the formation of the giant planets and their atmospheres when these data are combined with those that exist for Jupiter. 相似文献
3.
Upper limits are placed on the D/H ratio in the observed portions of the atmospheres of Jupiter and Saturn from observations at high S/N over the region of the 5-0 R(1) line of HD. The upper limits of 4 × 10?5 and 6 × 10?5 D/H on Jupiter and Saturn, respectively, are not inconsistent with present models for abundance ratios in the primitive solar nebula or with other estimates of this quantity from observations. 相似文献
4.
《Planetary and Space Science》1999,47(10-11):1201-1210
New models of Jupiter are based on observational data provided by the Galileo spaceprobe, which considerably improved previously existing estimates of the helium abundance in the atmosphere of Jupiter. These data yield for Jupiter’s atmosphere 20% of the solar oxygen abundance and do not agree with the results of the analysis of the collision of comet Shoemaker-Levy 9 with Jupiter (10 times the solar value). Therefore, both the models of Jupiter with water-depleted and water-enriched atmosphere are considered. By analogy with Jupiter, trial models of Saturn with a water-depleted external envelope are also developed. The molecular-metallic phase transition pressure of hydrogen Pm was taken to be 1.5, 2 and 3 Mbar. Since Saturn’s internal molecular envelope is noticeably enriched in the IR-component (its weight concentration, 0.25–0.30, being by a factor of 3–4 higher than in Jupiter), the phase transition pressure in Saturn can be lower than in Jupiter. In the constructed models, the IR-core masses are 3–3.5 M⊕ for Jupiter and 3–5.5 M⊕ for Saturn. Jupiter’s and Saturn’s IR-cores can be considered embryos onto which the accretion of the gas occurred during the formation of the planets. The mass of the hydrogen–helium component dispersed in the zone of planetary formation constitutes ≈2–5 planetary masses for Jupiter and ≈11–14 planetary masses for Saturn. 相似文献
5.
《Planetary and Space Science》1999,47(10-11):1183-1200
Interior models of Jupiter and Saturn are calculated and compared in the framework of the three-layer assumption, which rely on the perception that both planets consist of three globally homogeneous regions: a dense core, a metallic hydrogen envelope, and a molecular hydrogen envelope. Within this framework, constraints on the core mass and abundance of heavy elements (i.e. elements other than hydrogen and helium) are given by accounting for uncertainties on the measured gravitational moments, surface temperature, surface helium abundance, and on the inferred protosolar helium abundance, equations of state, temperature profile and solid/differential interior rotation. Results obtained solely from static models matching the measured gravitational fields indicate that the mass of Jupiter’s dense core is less than 14 M⊕ (Earth masses), but that models with no core are possible given the current uncertainties on the hydrogen–helium equation of state. Similarly, Saturn’s core mass is less than 22 M⊕ but no lower limit can be inferred. The total mass of heavy elements (including that in the core) is constrained to lie between 11 and 42 M⊕ in Jupiter, and between 19 and 31 M⊕ in Saturn. The enrichment in heavy elements of their molecular envelopes is 1–6.5, and 0.5–12 times the solar value, respectively. Additional constraints from evolution models accounting for the progressive differentiation of helium (Hubbard WB, Guillot T, Marley MS, Burrows A, Lunine JI, Saumon D, 1999. Comparative evolution of Jupiter and Saturn. Planet. Space Sci. 47, 1175–1182) are used to obtain tighter, albeit less robust, constraints. The resulting core masses are then expected to be in the range 0–10 M⊕, and 6–17 M⊕ for Jupiter and Saturn, respectively. Furthermore, it is shown that Saturn’s atmospheric helium mass mixing ratio, as derived from Voyager, Y=0.06±0.05, is probably too low. Static and evolution models favor a value of Y=0.11−0.25. Using, Y=0.16±0.05, Saturn’s molecular region is found to be enriched in heavy elements by 3.5 to 10 times the solar value, in relatively good agreement with the measured methane abundance. Finally, in all cases, the gravitational moment J6 of models matching all the constraints are found to lie between 0.35 and 0.38×10−4 for Jupiter, and between 0.90 and 0.98×10−4 for Saturn, assuming solid rotation. For comparison, the uncertainties on the measured J6 are about 10 times larger. More accurate measurements of J6 (as expected from the Cassini orbiter for Saturn) will therefore permit to test the validity of interior models calculations and the magnitude of differential rotation in the planetary interior. 相似文献
6.
《Planetary and Space Science》1999,47(10-11):1225-1242
Infrared spectra of Jupiter and Saturn have been recorded with the two spectrometers of the Infrared Space Observatory (ISO) in 1995–1998, in the 2.3–180 μm range. Both the grating modes (R=150–2000) and the Fabry-Pérot modes (R=8000–30,000) of the two instruments were used. The main results of these observations are (1) the detection of water vapour in the deep troposphere of Saturn; (2) the detection of new hydrocarbons (CH3C2H, C4H2, C6H6, CH3) in Saturn’s stratosphere; (3) the detection of water vapour and carbon dioxide in the stratospheres of Jupiter and Saturn; (4) a new determination of the D/H ratio from the detection of HD rotational lines. The origin of the external oxygen source on Jupiter and Saturn (also found in the other giant planets and Titan in comparable amounts) may be either interplanetary (micrometeoritic flux) or local (rings and/or satellites). The D/H determination in Jupiter, comparable to Saturn’s result, is in agreement with the recent measurement by the Galileo probe (Mahaffy, P.R., Donahue, T.M., Atreya, S.K., Owen, T.C., Niemann, H.B., 1998. Galileo probe measurements of D/H and 3He/4He in Jupiters atmosphere. Space Science Rev. 84 251–263); the D/H values on Uranus and Neptune are significantly higher, as expected from current models of planetary formation. 相似文献
7.
Wayne L. Slattery 《Icarus》1977,32(1):58-72
Planetary models for Jupiter and Saturn are computed using a fourth-order theory and a new molecular equation of state. The equation of state for the molecular hydrogen and helium planetary envelopes is taken from the Monte Carlo calculations of Slattery and Hubbard [Icarus 29, 187–192 (1976)]. Models for Jupiter are found that have a small amount of heavy elements either mixed with hydrogen and helium throughout the interior of the planet or concentrated in a small dense core. Saturn is modeled with a solar-composition hydrogen and helium envelope and a small derse core. We conclude that the molecular equation of state linked with suitable interior equations of state can produce Jovian models which satisfy the observational data. The planetary models show that the enrichment of heavy elements (relative to solar composition) is approximately 3 times for Jupiter and 10 times for Saturn. 相似文献
8.
Using a method defined in a previous paper [M. Combes and T. Encrenaz, Icarus39 1–27 (1979)], we reestimated the C/H ratio in the atmospheres of Jupiter and Saturn by the measurements of the weak visible CH4 bands, the CH4 3ν3 band, and the (3-0) and (4-0) quadrupole bands of H2. In the case of Jupiter we conclude that the C/H ratio is enriched by a factor ranging from 1.7 to 3.6 relative to the solar value. In the case of Saturn, our derived C/H value ranges from 1.2 to 3.2 times the solar value. The Jovian D/H ratio derived from this study is 1.2 × 10?5 < D/H < 3.1 × 10?5. The value derived for the D/H ratio on Saturn is not precise enough to be conclusive. 相似文献
9.
From an analysis of the Galileo Near Infrared Imaging Spectrometer (NIMS) data, Baines et al. (Icarus 159 (2002) 74) have reported that spectrally identifiable ammonia clouds (SIACs) cover less than 1% of Jupiter. Localized ammonia clouds have been identified also in the Cassini Composite Infrared Spectrometer (CIRS) observations (Planet. Space Sci. 52 (2004a) 385). Yet, ground-based, satellite and spacecraft observations show that clouds exist everywhere on Jupiter. Thermochemical models also predict that Jupiter must be covered with clouds, with the top layer made up of ammonia ice. For a solar composition atmosphere, models predict the base of the ammonia clouds to be at 720 mb, at 1000 mb if N/H were 4×solar, and at 0.5 bar for depleted ammonia of 10−2×solar (Planet. Space Sci. 47 (1999) 1243). Thus, the above NIMS and CIRS findings are seemingly at odds with other observations and cloud physics models. We suggest that the clouds of ammonia ice are ubiquitous on Jupiter, but that spectral identification of all but the freshest of the ammonia clouds and high altitude ammonia haze is inhibited by a combination of (i) dusting, starting with hydrocarbon haze particles falling from Jupiter's stratosphere and combining with an even much larger source—the hydrazine haze; (ii) cloud properties, including ammonia aerosol particle size effects. In this paper, we investigate the role of photochemical haze and find that a substantial amount of haze material can deposit on the upper cloud layer of Jupiter, possibly enough to mask its spectral signature. The stratospheric haze particles result from condensation of polycyclic aromatic hydrocarbons (PAHs), whereas hydrazine ice is formed from ammonia photochemistry. We anticipate similar conditions to prevail on Saturn. 相似文献
10.
High-resolution (0.1-Å) spectra of the 6815-Å band of methane are presented for Jupiter, Saturn, Uranus, and Neptune. Spectra for Uranus, Neptune, and the equatorial region of Saturn were acquired with the SPIFI (W. H. Smith, T. R. Hicks, and J. P. Born (1978). Proceedings of the 4th International Colloquium on Astrophysics, Triest, July 3–7, 1978. pp. 593–599) at the 2.2-m telescope of the Mauna Kea Observatory during May and June 1980. Additional spectra were obtained for Jupiter and the northern temperate and polar regions of Saturn in December 1980 and January 1981 from Kitt Peak National Observatory's McMath Solar Telescope. The spectra show a dichotomy in strength of methane absorption between Jupiter-Saturn and Uranus-Neptune. A simple model analysis, based on homogeneous scattering models, is unable to resolve whether this dichotomy is due to an actual increase in the methane mixing ratio with solar distance or to the temperature dependence of line strengths and absorption pathlengths in these atmospheres. If the rotational quantum number for the prominent 6818.9-Å feature is J < 4, then significant aerosol extinction must exist within the visibly accessible portion of Uranus' atmosphere for the methane mixing ratio to be greater than the solar value. 相似文献
11.
Ever since their discovery the regular satellites of Jupiter and Saturn have held out the promise of providing an independent set of observations with which to test theories of planet formation. Yet elucidating their origins has proven elusive. Here we show that Iapetus can serve to discriminate between satellite formation models. Its accretion history can be understood in terms of a two-component gaseous subnebula, with a relatively dense inner region, and an extended tail out to the location of the irregular satellites, as in the SEMM model of Mosqueira and Estrada (2003a,b) (Mosqueira, I., Estrada, P.R. [2003a]. Icarus 163, 198-231; Mosqueira, I., Estrada, P.R. [2003b]. Icarus 163, 232-255). Following giant planet formation, planetesimals in the feeding zone of Jupiter and Saturn become dynamically excited, and undergo a collisional cascade. Ablation and capture of planetesimal fragments crossing the gaseous circumplanetary disks delivers enough collisional rubble to account for the mass budgets of the regular satellites of Jupiter and Saturn. This process can result in rock/ice fractionation as long as the make up of the population of disk crossers is non-homogeneous, thus offering a natural explanation for the marked compositional differences between outer solar nebula objects and those that accreted in the subnebulae of the giant planets. For a given size, icy objects are easier to capture and to ablate, likely resulting in an overall enrichment of ice in the subnebula. Furthermore, capture and ablation of rocky fragments become inefficient far from the planet for two reasons: the gas surface density of the subnebula is taken to drop outside the centrifugal radius, and the velocity of interlopers decreases with distance from the planet. Thus, rocky objects crossing the outer disks of Jupiter and Saturn never reach a temperature high enough to ablate either due to melting or vaporization, and capture is also greatly diminished there. In contrast, icy objects crossing the outer disks of each planet ablate due to the melting and vaporization of water-ice. Consequently, our model leads to an enhancement of the ice content of Iapetus, and to a lesser degree those of Titan, Callisto and Ganymede, and accounts for the (non-stochastic) compositions of these large, low-porosity outer regular satellites of Jupiter and Saturn. For this to work, the primordial population of planetesimals in the Jupiter-Saturn region must be partially differentiated, so that the ensuing collisional cascade produces an icy population of ?1 m size fragments to be ablated during subnebula crossing. We argue this is likely because the first generation of solar nebula ∼10 km planetesimals in the Jupiter-Saturn region incorporated significant quantities of 26Al. This is the first study successfully to provide a direct connection between nebula planetesimals and subnebulae mixtures with quantifiable and observable consequences for the bulk properties of the regular satellites of Jupiter and Saturn, and the only explanation presently available for Iapetus’ low density and ice-rich composition. 相似文献
12.
R.F. Loewenstein D.A. Harper S.H. Moseley C.M. Telesco Harley A. Thronson R.H. Hildebrand S.E. Whitcomb R. Winston R.F. Stiening 《Icarus》1977,31(3):315-324
New broadband observations in several passbands between 30 and 500 μm of Mercury, Venus, Mars, Jupiter, Saturn, and Uranus are presented. The best agreement between the data and various thermal models of Mars, Jupiter, and Uranus is obtained with a slightly cooler absolute temperature scale than that previously adopted by Armstrong et al. (1972). The effective temperature of Uranus is 58 ± 2°K, which is in agreement with its solar equilibrium temperature. The existence of an internal energy source of Saturn has been reconfirmed and must lie within the range of 0.9 to 3.2 times the absorbed solar flux. A depression exists in the spectra of Jupiter, Saturn, and Uranus between 80 and 300 μm, which may be a result of NH3 opacity. 相似文献
13.
We present ground-based limb polarization measurements of Jupiter and Saturn consisting of full disk imaging polarimetry for the wavelength 7300 Å and spatially resolved (long-slit) spectropolarimetry covering the wavelength range 5200-9350 Å.For the polar region of Jupiter we find for λ = 6000 Å a very strong radial (perpendicular to the limb) fractional polarization with a seeing corrected maximum of about +11.5% in the South and +10.0% in the North. This indicates that the polarizing haze layer is thicker at the South pole. The polar haze layers extend down to 58° in latitude. The derived polarization values are much higher than reported in previous studies because of the better spatial resolution of our data and an appropriate consideration of the atmospheric seeing. Model calculations demonstrate that the high limb polarization can be explained by strongly polarizing (p ≈ 1.0), high albedo (ω ≈ 0.98) haze particles with a scattering asymmetry parameter of g ≈ 0.6 as expected for aggregate particles of the type described by West and Smith (West, R.A., Smith, P.H. [1991]. Icarus 90, 330-333). The deduced particle parameters are distinctively different when compared to lower latitude regions.The spectropolarimetry of Jupiter shows a decrease in the polar limb polarization towards longer wavelengths and a significantly enhanced polarization in strong methane bands when compared to the adjacent continuum. This is a natural outcome for a highly polarizing haze layer above an atmosphere where multiple scatterings are suppressed in absorption bands. For lower latitudes the fractional polarization is small, negative, and it depends only little on wavelength except for the strong CH4-band at 8870 Å.The South pole of Saturn shows a lower polarization (p ≈ 1.0-1.5%) than the poles of Jupiter. The spectropolarimetric signal for Saturn decrease rapidly with wavelength and shows no significant enhancements in the fractional polarization in the absorption bands. These properties can be explained by a vertically extended stratospheric haze region composed of small particles <100 nm as suggested previously by Karkoschka and Tomasko (Karkoschka, E., Tomasko, M. [2005]. Icarus 179, 195-221).In addition we find in the V- and R-band a previously not observed strong polarization feature (p = 1.5-2.0%) near the equator of Saturn. The origin of this polarization signal is unclear but it could be related to a seasonal effect.Finally we discuss the potential of ground-based limb polarization measurements for the investigation of the scattering particles in the atmospheres of Jupiter and Saturn. 相似文献
14.
Allen S. Grossman James B. Pollack Ray T. Reynolds Audrey L. Summers Harold C. Graboske 《Icarus》1980,42(3):358-379
We have calculated evolutionary and static models of Jupiter and Saturn with homogeneous solar composition mantles and dense cores of material consisting of solar abundances of SiO2, MgO, Fe, and Ni. Evolutionary sequences for Jupiter were calculated with cores of mass 2, 4, 6, and 8% of the Jovian mass. Evolutionary sequences for Saturn were calculated with cores of mass 16, 18, 20, and 22% of total mass. Two envelope mixtures, representative of the solar abundances were used: X (mass fraction of hydrogen) = 0.74, Y (mass fraction of helium) = 0.24 and X = 0.77 and Y = 0.21. For Jupiter, the observations of the temperature at 1 bar pressure (T1bar), radius and internal luminosity were best fit by evolutionary models with a core mass of ～6.5% and chemical composition of X = 0.77, Y = 0.21. The calculated cooling time for Jupiter is approximately 4.9 × 109 years, which is consistent, within our error bars, with the known age of the solar system. For Saturn, the observations of the radius, internal luminosity and T1BAR can be best fit by evolutionary models with a core mass of ～21% and chemical composition of X = 0.77, Y = 0.21. The cooling time calculated for Saturn is approximately 2.6 × 109 years, almost a factor 2 less than the present age of the solar system. Static models of Jupiter and Saturn were calculated for the above chemical compositions in order to investigate the sensitivity of the calculated gravitational moments, J2 and J4, to the mass of the dense core, T1BAR and hydrogen/helium ratio. We find for Jupiter that a model having a core mass of approximately 7% gives values of J2, J4, and T1BAR that are within observational limits, for the mixture X = 0.77, Y = 0.21. The static Jupiter models are completely consistent with the evolutionary results. For Saturn, the quantities J2, J4, and J6 determined from the static models with the most probable T1BAR of 140°K, using modeling procedures which result in consistent models for Jupiter, are considerably below the observed values. 相似文献
15.
The giant planetary magnetospheres surrounding Jupiter and Saturn respond in quite different ways, compared to Earth, to changes in upstream solar wind conditions. Spacecraft have visited Jupiter and Saturn during both solar cycle minima and maxima. In this paper we explore the large-scale structure of the interplanetary magnetic field (IMF) upstream of Saturn and Jupiter as a function of solar cycle, deduced from solar wind observations by spacecraft and from models. We show the distributions of solar wind dynamic pressure and IMF azimuthal and meridional angles over the changing solar cycle conditions, detailing how they compare to Parker predictions and to our general understanding of expected heliospheric structure at 5 and 9 AU. We explore how Jupiter’s and Saturn’s magnetospheric dynamics respond to varying solar wind driving over a solar cycle under varying Mach number regimes, and consider how changing dayside coupling can have a direct effect on the nightside magnetospheric response. We also address how solar UV flux variability over a solar cycle influences the plasma and neutral tori in the inner magnetospheres of Jupiter and Saturn, and estimate the solar cycle effects on internally driven magnetospheric dynamics. We conclude by commenting on the effects of the solar cycle in the release of heavy ion plasma into the heliosphere, ultimately derived from the moons of Jupiter and Saturn. 相似文献
16.
Moist convective storms constitute a key aspect in the global energy budget of the atmospheres of the giant planets. Among them, Saturn is known to develop the largest scale convective storms in the Solar System, the Great White Spots (GWS) which occur rarely and have been detected once every 30 years approximately. On the average, Saturn seems to show much less convective storms than Jupiter with smaller size and reduced frequency and intensity. Here we present detailed simulations of the onset and development of storms at the Equator and mid-latitudes of Saturn. These are the regions where most of the recent convective activity of the planet has been observed. We use a 3D anelastic model with parameterized microphysics (Hueso and Sánchez-Lavega, 2001, Icarus 151, 257) studying the onset and evolution of water and ammonia moist convective storms up to sizes of a few hundred km. Water storms, while more difficult to initiate than in Jupiter, can be very energetic, arriving to the 150 mbar level and developing vertical velocities on the order of 150 m s−1. Ammonia storms develop easier but with a much smaller intensity unless very large abundances of ammonia (10 times solar) are present in Saturn's atmosphere. The Coriolis forces play a major role in the morphology and properties of water based storms. 相似文献
17.
The hypothesis on the genetic connection of near-parabolic comets with Jupiter, Saturn, and the transPlutonian region (5–3000
AU) proposed by E.M. Drobyshevskii is considered. It has been shown that, on average, 5.6 comets per an area of 106 AU2 passed through the transPlutonian region during the whole history of observations. Six-hundred nineteen comets crossed the
ecliptic at heliocentric distances ranging from 0 to 2 AU. As has been shown, from the total number of 945 near-parabolic
comets, eight comets closely approached Jupiter and five closely approached Saturn. The Kreutz comets, 1277 objects, did not
approach Jupiter closer than 3 AU. Their minimal distance to Saturn was 5.5 AU. The minimal distance of the Kreutz comets
from the edge of the transPlutonian region was 28.8 AU. The analysis led to the conclusion that the concept on the origin
of the near-parabolic comets suggested by Drobyshevskii is groundless. 相似文献
18.
19.
A. V. Morozhenko 《Kinematics and Physics of Celestial Bodies》2007,23(6):245-257
Based on the data on the wavelength dependence of geometrical albedo for the disks of Jupiter and Saturn, we determined the trends in the height variation of the aerosol optical depth in the upper atmospheric layers of these planets, the fractional methane concentration in the Jovian atmosphere (0.00125), and the monochromatic methane absorption coefficients (or the superposition of these coefficients for methane and ammonia) typical of the thermal conditions in the atmospheres of Jupiter and Saturn in the wavelength range from 527 to 956 nm. 相似文献
20.
Three-dimensional numerical simulations show that large-scale latent heating resulting from condensation of water vapor can produce multiple zonal jets similar to those on the gas giants (Jupiter and Saturn) and ice giants (Uranus and Neptune). For plausible water abundances (3-5 times solar on Jupiter/Saturn and 30 times solar on Uranus/Neptune), our simulations produce ∼20 zonal jets for Jupiter and Saturn and 3 zonal jets on Uranus and Neptune, similar to the number of jets observed on these planets. Moreover, these Jupiter/Saturn cases produce equatorial superrotation whereas the Uranus/Neptune cases produce equatorial subrotation, consistent with the observed equatorial-jet direction on these planets. Sensitivity tests show that water abundance, planetary rotation rate, and planetary radius are all controlling factors, with water playing the most important role; modest water abundances, large planetary radii, and fast rotation rates favor equatorial superrotation, whereas large water abundances favor equatorial subrotation regardless of the planetary radius and rotation rate. Given the larger radii, faster rotation rates, and probable lower water abundances of Jupiter and Saturn relative to Uranus and Neptune, our simulations therefore provide a possible mechanism for the existence of equatorial superrotation on Jupiter and Saturn and the lack of superrotation on Uranus and Neptune. Nevertheless, Saturn poses a possible difficulty, as our simulations were unable to explain the unusually high speed (∼) of that planet’s superrotating jet. The zonal jets in our simulations exhibit modest violations of the barotropic and Charney-Stern stability criteria. Overall, our simulations, while idealized, support the idea that latent heating plays an important role in generating the jets on the giant planets. 相似文献