Galileo Probe Entry Research Articles

The Spatial Variation of Water Clouds, NH3, and H2O on Jupiter Using Keck Data at 5 Microns

We obtained high-resolution spectra of Jupiter between 4.6 and 5.4 µm using NIRSPEC on the Keck 2 telescope in February 2017. We measured the spatial variation of NH3, H2O, and the pressure level of deep (p > 3 bar) clouds using two geometries. We aligned the slit north–south on Jupiter’s Central Meridian to measure the spatial variation of the gas composition and cloud structure between 66°N and 70°S. With the slit aligned east–west, we also examined the longitudinal variation at two regions of the North Equatorial Belt (NEB) at 18°N and at 8°N near the latitude of the Galileo Probe entry site. We used the integrated line absorption, also known as the equivalent width, of deuterated methane (CH3D) at 4.66 µm to derive the pressure level of deep clouds between 3 and 7 bar. From thermochemical models, these are most likely water clouds. At the location of a deep cloud revealed by HST methane-band imaging, we found spectroscopic evidence for an opaque cloud at the 5 bar level. We also identified regions on Jupiter that lacked deep clouds but exhibited evidence for upper clouds and enhanced NH3. We estimated column-averaged mole fractions of H2O and NH3 above the opaque lower boundary of the deep cloud. The meridional scan exhibited significant belt-zone structure with retrieved NH3 abundances in the 200–400 ppm range above the opaque lower cloud, except for a depletion (down to 90 ppm) in the NEB. Water in Jupiter’s belts varies from a maximum of 7 ppm at 8°S to a minimum of 1.5 ppm at 23°S. We found evidence for water clouds and enhanced NH3 and H2O in the South Equatorial Belt Outbreak region at 13°S. The NEB is a heterogeneous region with significant variation in all of these quantities. The NH3 abundance at 18°N and 8°N varies with the longitude with mole fractions between 120 and 300 ppm. The H2O abundance at these same latitudes varies with the longitude with mole fractions between 3 and 10 ppm. Our volatile mole fractions apply to the 5 to 8 bar pressure range (or to the level of an opaque cloud top where found at shallower pressure); therefore, they imply a deeper gradient continuing to increase toward higher concentrations detected by the Galileo Probe Mass Spectrometer at 11 and 20 bar. Hot Spots in the NEB exhibit minimal cloud opacity; however, they lack prominent anomalies in the concentrations of NH3 or H2O.

Investigation of Galileo Probe Entry Heating with Coupled Radiation and Ablation

This paper presents a trajectory-based heating and ablation study of the Galileo probe forebody flow and thermal protection system performance. The validity of modeling assumptions regarding diffusion, radiative heating, and ablation made in previous work, including preflight predictions, are addressed. The Navier–Stokes equations are solved assuming a one-temperature chemical nonequilibrium flowfield with coupled radiation and ablation. Geometric changes in the forebody due to ablation are accounted for. Solving the Stefan–Maxwell equations to compute the species mass diffusion in the flowfield, instead of assuming a constant Schmidt number as was done in previous studies, was found to significantly increase total predicted recession by about 10% on the flank, due to increased convective heating. Application of the high-fidelity ray-tracing approach resulted in a 10% reduction in the radiative heating along the forebody when compared with the heritage tangent-slab approximation. Additional modeling approaches, such as state-specific H modeling, application of ray-tracing for coupled flowfield radiative source terms, and including precursor absorption were considered but found to have a minimal impact on recession. The resulting nominal prediction was found to be nearly within the uncertainty of the flight data along the entire surface of the probe. This improved agreement relative to past studies is due to the notable impact of shape change, multicomponent diffusion, and ray-tracing radiative heating, most of which were not included in previous models. To provide uncertainty bounds for the present simulations, an uncertainty analysis was performed. Sources of uncertainty were identified in the ablation modeling, radiation modeling, flowfield kinetics, turbulence modeling, and thermodynamic properties of select species. When the impact of all considered uncertainties are combined, the stagnation point recession varies between and of the nominal value while a near constant uncertainty band exists on the flank.

Fresh clouds: A parameterized updraft method for calculating cloud densities in one-dimensional models

Models of cloud condensation under thermodynamic equilibrium in planetary atmospheres are useful for several reasons. These equilibrium cloud condensation models (ECCMs) calculate the wet adiabatic lapse rate, determine saturation-limited mixing ratios of condensing species, calculate the stabilizing effect of latent heat release and molecular weight stratification, and locate cloud base levels. Many ECCMs trace their heritage to Lewis (Lewis, J.S. [1969]. Icarus 10, 365–378) and Weidenschilling and Lewis (Weidenschilling, S.J., Lewis, J.S. [1973]. Icarus 20, 465–476). Calculation of atmospheric structure and gas mixing ratios are correct in these models.We resolve errors affecting the cloud density calculation in these models by first calculating a cloud density rate: the change in cloud density with updraft length scale. The updraft length scale parameterizes the strength of the cloud-forming updraft, and converts the cloud density rate from the ECCM into cloud density. The method is validated by comparison with terrestrial cloud data.Our parameterized updraft method gives a first-order prediction of cloud densities in a “fresh” cloud, where condensation is the dominant microphysical process. Older evolved clouds may be better approximated by another 1-D method, the diffusive–precipitative Ackerman and Marley (Ackerman, A.S., Marley, M.S. [2001]. Astrophys. J. 556, 872–884) model, which represents a steady-state equilibrium between precipitation and condensation of vapor delivered by turbulent diffusion.We re-evaluate observed cloud densities in the Galileo Probe entry site (Ragent, B. et al. [1998]. J. Geophys. Res. 103, 22891–22910), and show that the upper and lower observed clouds at ∼0.5 and ∼3bars are consistent with weak (cirrus-like) updrafts under conditions of saturated ammonia and water vapor, respectively. The densest observed cloud, near 1.3bar, requires unexpectedly strong updraft conditions, or higher cloud density rates. The cloud density rate in this layer may be augmented by a composition with non-NH4SH components (possibly including adsorbed NH3).

Multiband Radiation Model for Simulation of Galileo Probe Entry Flowfield

Received 4 March 2005; revision received 1 October 2005; accepted for publication 3 October 2005. Copyright c © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0887-8722/06 $10.00 in correspondence with the CCC. ∗Researcher, Computational Science Research Group, Institute of Aerospace Technology; smatsu@chofu.jaxa.jp. Member AIAA. †Graduate Student, Department of Aerospace Engineering. ‡Research Associate, Department of Aerospace Engineering. Member AIAA. §Professor, Institute of Fluid Science, Sendai 980-8577. Associate Fellow AIAA. ¶Professor, Department of Aerospace Engineering. Associate Fellow AIAA. revealed that there was a significant discrepancy of the final recession profile from that given by the preflight prediction. Indeed, the amount of recession occurred at the stagnation region deduced from the flight data was almost three-fourths and that at the frustum region was almost double when compared with those given by the preflight prediction.2 This discrepancy has yet to be explained. Recently, in our previous study,3 we succeeded in reproducing the large recession occurring at the frustum region and gave one consistent explanation for why the radiative heat flux along the frustum region of the Galileo probe was larger than the preflight predictions. It was found that the number densities of radiation-absorbing carbonaceous species in the ablation layer were substantially decreased by excessive diffusion and dissociation reactions caused by the enhanced turbulence effects. To obtain this result, an accurate calculation of a strongly radiating flowfield over the Galileo probe that accounted for detailed spectral radiative properties was used. The line-by-line method4 is known to yield the most accurate spectral radiative properties of high-temperature gases. However, it is not suitable for coupling with a flowfield calculation because of its enormous computational load. The modern multiband radiation models can reduce the computing time of the line-by-line calculation at least by a factor of 100 and reproduce the line-by-line result within a small error.5,6 In these models, it is customary to assume that the absorption coefficients depend only on temperature, assuming in advance typical electron number densities within the shock layer. This treatment, however, is not suitable for the Galileo probe entry case because the line shape of atomic hydrogen has significant dependence on electron number density. In this study, therefore, we give a new implementation of the radiation multiband model that depends on both the local temperature and electron number density.

Water, ammonia, and H 2S mixing ratios in Jupiter's five-micron hot spots: A dynamical model

The Galileo probe entered the jovian atmosphere at the southern edge of a 5-micron hot spot, one of typically 8–10 quasi-evenly-spaced longitudinal areas of anomalously high 5-micron IR emission that reside in a narrow latitude band centered on +7.5 degrees. These hot spots are characterized primarily by a low abundance of the cloud particles that dominate the 5-micron opacity at other locations on the planet, and by significant desiccation of ammonia, water and hydrogen sulfide in the upper layers of the troposphere. Ortiz et al. [1998. Evolution and persistence of 5-micron hot spots at the Galileo probe entry latitude. J. Geophys. Res. 103, 23,051–23,069] found that the latitude and drift rate of the hot spots could be explained if they are formed by an equatorially trapped Rossby wave of meridional degree 1 moving with a phase speed between 99 and 103 m s −1 relative to System III. Here we model additional properties of the hot spots in terms of the amplitude saturation of such a wave propagating in the weakly stratified deep troposphere. We identify the hot spots with locations where the wave plus mean thermal stratification becomes marginally stable. In these locations, potential temperature isotherms stretch downward to very deep levels in the troposphere. Since fluid parcels follow these isotherms under adiabatic flow conditions, the parcels dive downward when they enter the portion of the wave associated with the hot spot and soar upward upon leaving the spot. We show that this model can account for the anomalous vertical profiles of NH 3, H 2O, and H 2S mixing ratio measured by the Galileo probe. Pressures vary by as much as 20 bar over potential temperature isotherms in solutions that produce sufficient desiccation of water and H 2S in hot spots. Approximately 6 × 10 −2 of Jupiter's internal heat flux must be tapped to maintain the wave over the mean hot spot lifetime of 10 7 s. The results suggest that the phenomenon that causes hot spots may occur widely, although in less dramatic form, across Jupiter's surface, and consequently NH 3, H 2S, and H 2O mixing ratio profiles may vary significantly from location to location in Jupiter's troposphere.

Numerical Simulation of Galileo Probe Entry Flowfield with Radiation and Ablation

A trajectory-based heating analysis of the Galileo probe entry flowfield is attempted to reproduce the heat-shield recession data obtained during the entry flight. In the calculation, the mass conservation equations for the freestream gas (hydrogen-helium gas mixture) and the ablation product gas are solved with an assumption of thermochemical equilibrium. The ablation process is assumed to be quasi steady and is coupled with the flowfield calculation. The radiative energy transfer calculation is tightly coupled with the flowfield calculation, where the absorption coefficients of the gas mixture are given by the multiband radiation model having 4781 wavelength points for wavelength range from 750 to 15,000 A. The injection-induced turbulence model proposed by Park is employed to account for the enhanced turbulence effect due to the ablation product gas

The Stratification of Jupiter's Troposphere at the Galileo Probe Entry Site

Galileo Probe Atmospheric Structure Investigation (ASI) pressure and temperature sensor data acquired during the parachute descent phase have been used to derive the static stability structure of Jupiter's troposphere at pressure levels of 0.5–22 bars using three techniques. The first approach utilizes both the p-sensor and T-sensor data, but since the p-sensor's zero offset was significantly affected by the thermal anomaly in the probe, two other approaches using only T-sensor data have also been developed. By making the physically reasonable assumptions of equilibrium descent for the probe and hydrostatic balance of the atmosphere, an algorithm for deriving the background static stability from T-sensor measurements alone is developed. Regions with static stability 0.1–0.2 K km −1 are found at 0.5–1.7 bars, 3–8.5 bars, and 14–20 bars. Between these layers, regions of weaker static stability are present. Mean molecular weight gradients due to the vertical variation of water vapor abundance near the 11-bar pressure level appear to stabilize the atmosphere at this level. Oscillatory structures with vertical wavelength ∼15–30 km and amplitude ∼0.1–0.2 K are observed in the T-sensor data. For pressure <2 bars, these eddies are well above the noise level of the measurements and are consistent with the predictions of linear gravity wave theory for a wave with horizontal phase speed c x =160 m s −1 with respect to System III propagating through the static stability derived from the T-sensor data alone. They provide quantitative confirmation of the static stability derived from T-sensor data in the troposphere where p<2 bars. The observed static stability structure shows an inverse correlation with the regions of wind shear observed by the Doppler Wind Experiment: regions of highest shear in the horizontal wind appear to be associated with regions of lowest static stability. The particulate population detected by other experiments on the probe shows some correlation with the uppermost layer of static stability, suggesting enhanced solar energy deposition at these levels may play a role in producing the positive static stability.

Galileo: Close-up Views of Jupiter’s Dynamic Atmosphere

AbstractThe Galileo spacecraft’s Solid State Imager (SSI) has been returning mosaics of Jupiter since 1996. The combination of high spatial resolution, broad spectral range, and short mosaic time steps has revealed a dynamic, vertically extended cloud structure not detectable by Voyager. These data have stimulated new analyses of major features such as zonal jets, the Great Red Spot, White Ovals, and the Galileo Probe entry site. Near-infrared images have provided fundamental constraints on the vertical structure of clouds and hazes, including the first imaging of a water cloud. Results from night side imaging include an extensive search for lightning, the first matching of lightning events to day side storm clouds, and the first spectral and spatial measurements of visible-wavelength auroral phenomena (not discussed here, see Vasavada et al. 2000). The identification of several tall, energetic storm systems at specific latitudes has led to new ideas about the role of moist convection in Jupiter’s atmospheric energetics.

Structure of the Jovian Stratosphere at the Galileo Probe Entry Site

The structure of the Jovian stratosphere at the Galileo probe entry site is investigated through calculations of radiative heating rates based on measurements of the temperature profile, composition, and aerosol distribution. From analysis of mid-IR observations of Jupiter, we determine a C 2H 2 mole fraction of 1.1– 4.3× 10 −6 at 0.01 mbar, and a C 2H 6 mole fraction of 2.8– 6.5× 10 −6 at 0.4–10 mbar. The derived distributions imply that C 2H 6 and C 2H 2 are the most important coolants in the Jovian stratosphere from 0.004 to 10 mbar, and that the stratosphere is close to radiative equilibrium. In Jupiter's stratosphere, as in the stratosphere of the Earth, photochemical species play an essential role in the energy balance.

Reconciling Galileo Probe Data and Ground-Based Radio Observations of Ammonia on Jupiter

Prior to the Galileo probe entry in Jupiter's atmosphere, the ammonia abundance in the planet's deep atmosphere as deduced from microwave observations was thought to be close to the solar N value at P>3 bar and subsolar at P<2 bar. Analysis of the attenuation of the probe radio signal during its descent in Jupiter's atmosphere suggested NH 3 to be 3.6±0.5 times solar N at P>8 bar (Folkner et al. 1998). Assuming this high value is globally representative of the NH 3 abundance in Jupiter's deep atmosphere, we show in this article that to match Jupiter's microwave spectrum the ammonia abundance must, globally, decrease at pressures P≲4 bar, and reach subsolar (≲0.5) values at P≲2 bar. We confirm earlier analysis of the 1.3-cm wavelength region indicating that the disk-averaged relative humidity must be of the order of 10% at P<0.55 bar. We discuss various ways in which NH 3 could decrease globally at altitudes well below the level where the NH 3-ice clouds form. We also present radio images of Jupiter taken with the VLA at 2, 3.6, and 6 cm wavelength in November/December 1995 and January 1996. The Galileo probe entered Jupiter's atmosphere on 7 December 1995, at a latitude of 6.5°N, i.e., at the southern edge of the north equatorial belt (NEB). Simulations of our data suggest that the longitude-averaged NH 3 abundance in the NEB at the time of the Galileo probe entry is of the order of 50–70% of the value in the equatorial zone (EZ), while the NH 3 abundance in the EZ is about ≲0.5×solar N. This low ammonia abundance in the NEB must extend down to the ∼4- to 6-bar level.

A comparison of the atmospheres of Jupiter and Saturn: deep atmospheric composition, cloud structure, vertical mixing, and origin

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 condensible 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.

The planet Jupiter

The exploration of Jupiter, the closest and biggest giant planet, has provided key information about the origin and evolution of the outer Solar system. Our knowledge has strongly benefited from the Voyager and Galileo space missions. We now have a good understanding of Jupiter's thermal structure, chemical composition and magnetospheric environment. There is still debate about the nature of the heating source responsible for the high thermospheric temperatures (precipitating particles and/or gravity waves). The measurement of elemental abundance ratios (C/H, N/H, S/H) gives strong support to the “nucleation” formation model, according to which giant planets formed from the accretion of an initial core and the collapse of the surrounding gaseous protosolar nebula. The D/H and $^3$ He/ $^4$ He ratios are found to be representative of their protosolar value. The helium abundance, in contrast, appears to be slightly depleted in the outer envelope with respect to the protosolar value; this departure is interpreted as an evolutionary effect, due to the condensation of helium droplets in the liquid hydrogen ocean inside Jupiter's interior. The cloud structure of Jupiter, characterized by the belt-zone system, is globally understood; also present are specific features like regions of strong infrared radiation (“hot spots”), colder regions (“white ovals”) and the Great Red Spot (GRS). Clouds were surprisingly absent at the hot spot corresponding to the Galileo probe entry site, and the water abundance measured there was strongly depleted with respect to the solar O/H value. This probably implies that hot spots are dry, cloud-free regions of subsidence, while “normal” air, rich in condensibles, is transported upward by convective motions. As a result, the Jovian meteorology, still based on Halley-type cells, seems to be much more complex than a simple zone-belt system. The nature of the GRS, a giant anticyclonic storm, colder and higher than its environment, has been confirmed by the Galileo observations, but its internal structure appears to be very complex. Strong winds, probably driven by the Jovian internal source, were measured at deep tropospheric levels. The troposphere might be statically stable at pressures higher than 18 bars, but the extent of this putative radiative layer is still unknown.

Characteristics of the Galileo probe entry site from Earth‐based remote sensing observations

A reassessment of ground‐based observations confirms to better than a 98% confidence level that the Galileo probe entered a 5‐μm hot spot, a region of unusual clarity and dryness, some 900±300 km north of its southern boundary. Cloud conditions at that point were similar to those in the center of this region, some 600 km further north. At the time of the probe entry, the region was evolving to a slightly larger size and even thinner cloud conditions, as evidenced by its rapidly brightening appearance at 4.78 μm. The low reflectivity of the region in red light is highly anticorrelated with 4.78‐μm thermal emission, but this correlation breaks down in the blue. In general, the reflectivity of most hot spots is remarkably uniform, although the 4.78‐μm thermal emission is highly variable. A cloud structure most consistent with both the observed reflected sunlight and thermal emission properties consists of two layers: (1) a cloud layer above the 450‐mbar level extending up to the 150‐mbar level that probably consists of submicron sized particles and (2) a tropospheric cloud that is probably below the 1‐bar level, possibly ammonia hydrosulfide, with low optical thickness in the infrared. A population of particles larger than ∼3 μm, clearly present at the NH3 ice cloud level outside hot spots, is absent inside them. The NH3 gas abundance near 300–400 mbar pressure does not appear to be unusually depleted in hot spots. Zonal structures in the tropospheric temperature field near the probe entry site were not correlated with the location of 5‐μm hot spots but moved at speeds closer to the internal rotation rate of the planet. The properties of the tropospheric thermal waves at the probe entry latitude show little correlation to the properties of the 5‐μm hot spot waves. Temperatures at the probe entry site derived from remote sensing are warmer than the Atmospheric Structure Instrument (ASI) experiment results near the tropopause, probably because the low‐temperature ASI features are confined to regions smaller than the ∼6000‐km resolution characteristic of the remote sensing.

Evolution and persistence of 5‐μm hot spots at the Galileo probe entry latitude

We present a study on the longitudinal locations, morphology, and evolution of the 5‐μm hot spots at 6.5°N latitude (planetocentric) from an extensive Infrared Telescope Facility‐National Science Foundation Camera (IRTF‐NSFCAM) data set spanning more than 3 years, which includes the date of the Galileo probe entry. A probabilistic analysis of the data shows that within periods of several months to even more than a year, there are eight or nine longitudinal areas with high likelihood of containing a 5‐μm hot spot. These areas drift together with respect to System III at a rate which changes only slowly in time, and they are quasi evenly spaced, suggesting a wave feature. A spectral analysis of the radiance data reveals that planetary wavenumbers 8, 9, and 10 are predominant in the data, 10 having more spectral power in several time periods when the speed was 103.5–102.5 m/s, while planetary wavenumber 8 has much more power when the speed is (99.5±0.5) m/s. By using the Galileo probe zonal wind speed [Atkinson et al., 1997] at the level of the main cloud that is opaque to the radiation at 5 μm (∼2 bar), our drift corrections imply a westward phase speed for the proposed wave. The wavenumbers and phase speeds are found to be consistent with an equatorial Rossby wave, and the dispersive properties of this wave can account for the observed simultaneous changes in the dominant wavenumber and drift speed. We take advantage of this interpretation to infer properties of the vertical structure at 6.5°N.

Galileo Imaging of Jupiter's Atmosphere: The Great Red Spot, Equatorial Region, and White Ovals

During the first six orbits of the Galileo spacecraft's prime mission, the Solid State Imaging (SSI) system acquired multispectral image mosaics of Jupiter's Great Red Spot, an equatorial belt/zone boundary, a “5-μm hot spot” similar to the Galileo Probe entry site, and two of the classic White Ovals. We present mosaics of each region, approximating their appearance at visible wavelengths and showing cloud height and opacity variations. The local wind field is derived by tracking cloud motions between multiple observations of each region with time separations of roughly 1 and 10 hr. Vertical cloud structure is derived in a companion paper by Banfieldet al. (Icarus135, 230–250). Galileo's brief, high-resolution observations complement Earth-based and Voyager studies and offer local meteorological context for the Galileo Probe results. Our results show that the dynamics of the zonal jets and large vortices have changed little since Voyager, with a few exceptions. We detect a cyclonic current within the center of the predominantly anticyclonic Great Red Spot. The zonal velocity difference between 0° S and 6° S has increased by 20 m sec−1. We measure a strong northeast flow approaching the hot spot. This flow indicates either massive horizontal convergence or the presence of a large anticyclonic vortex southeast of the hot spot. The current compact arrangement of two White Ovals and a cyclonic structure greatly perturbs the zonal jets in that region.

Vertical Structure of Jupiter's Atmosphere at the Galileo Probe Entry Latitude

The vertical structure of Jupiter's atmosphere is examined to better characterize the latitudinal region of the Galileo probe entry site: +5°–10° planetographic latitude. One-hundred Hubble Space Telescope images of Jupiter taken with the 893- and 953-nm filters on 13 and 17 February 1995, 5 October 1995, and 14 May 1996 are analyzed, and a two-cloud model of the jovian atmosphere (D. M. Kuehn and R. F. Beebe 1993,Icarus101,282–292) is used to interpret center-to-limb variations of bright plume heads and adjacent dark areas in the latitude region +2°–10°. For both the plume heads and dark areas, the top of the ammonia cloud deck reaches a pressure level of roughly 200 mbar, and the cloud has an optical depth of between 6 and 7. The optical depth of the stratospheric haze layer is 0.59 for the plumes and 0.34 for the dark regions, while the single scattering albedo of the ammonia cloud deck is 0.996 for the plumes and 0.950 for the dark regions. Sensitivity tests motivated by the preliminary results from the Galileo probe net flux radiometer and nephelometer experiments indicate that the ammonia cloud deck may have a patchy structure.

Earth-Based Observations of the Galileo Probe Entry Site

Earth-based observations of Jupiter indicate that the Galileo probe probably entered Jupiter's atmosphere just inside a region that has less cloud cover and drier conditions than more than 99 percent of the rest of the planet. The visual appearance of the clouds at the site was generally dark at longer wavelengths. The tropospheric and stratospheric temperature fields have a strong longitudinal wave structure that is expected to manifest itself in the vertical temperature profile.