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1.
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 NH3, H2O, and H2S 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 H2S 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 107 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 NH3, H2S, and H2O mixing ratio profiles may vary significantly from location to location in Jupiter's troposphere.  相似文献   

2.
The in situ measurements of the Galileo Probe Mass Spectrometer (GPMS) were expected to constrain the abundances of the cloud-forming condensible volatile gases: H2O, H2S, and NH3. However, since the probe entry site (PES) was an unusually dry meteorological system—a 5-μm hotspot—the measured condensible volatile abundances did not follow the canonical condensation-limited vertical profiles of equilibrium cloud condensation models (ECCMs) such as Weidenschilling and Lewis (1973, Icarus 20, 465-476). Instead, the mixing ratios of H2S and NH3 increased with depth, finally reaching well-mixed equilibration levels at pressures far greater than the lifting condensation levels, whereas the mixing ratio of H2O in the deep well-mixed atmosphere could not be measured. The deep NH3 mixing ratio (with respect to H2) of (6.64±2.54)×10−4 from 8.9-11.7 bar GPMS data is consistent with the NH3 profile from probe-to-orbiter signal attenuation (Folkner et al., 1998, J. Geophys. Res. 103, 22847-22856), which had an equilibration level of about 8 bar. The GPMS deep atmosphere H2S mixing ratio of (8.9±2.1)×10−5 is the only measurement of Jupiter's sulfur abundance, with a PES equilibration level somewhere between 12 and 15.5 bar. The deepest water mixing ratio measurement is (4.9±1.6)×10−4 (corresponding to only about 30% of the solar abundance) at 17.6-20.9 bar, a value that is probably much smaller than Jupiter's bulk water abundance. The 15N/14N ratio in jovian NH3 was measured at (2.3±0.3)×10−3 and may provide the best estimate of the protosolar nitrogen isotopic ratio. The GPMS methane mixing ratio is (2.37±0.57)×10−3; although methane does not condense on Jupiter, we include its updated analysis in this report because like the condensible volatiles, it was presumably brought to Jupiter in icy planetesimals. Our detailed discussion of calibration and error analysis supplements previously reported GPMS measurements of condensible volatile mixing ratios (Niemann et al., 1998, J. Geophys. Res. 103, 22831-22846; Atreya et al., 1999, Planet. Space Sci. 47, 1243-1262; Atreya et al., 2003, Planet. Space Sci. 51, 105-112) and the nitrogen isotopic ratio (Owen et al., 2001b, Astrophys. J. Lett. 553, L77-L79). The approximately three times solar abundance of NH3 (along with CH4 and H2S) is consistent with enrichment of Jupiter's atmosphere by icy planetesimals formed at temperatures <40 K (Owen et al., 1999, Nature 402 (6759), 269-270), but would imply that H2O should be at least 3×solar as well. An alternate model, using clathrate hydrates to deliver the nitrogen component to Jupiter, predicts O/H?9×solar (Gautier et al., 2001, Astrophys. J. 550 (2), L227-L230). Finally we show that the measured condensible volatile vertical profiles in the PES are consistent with column-stretching or entraining downdraft scenarios only if the basic state (the pre-stretched column or the entrainment source region) is described by condensible volatile vertical profiles that are drier than those in the equilibrium cloud condensation models. This dryness is supported by numerous remote sensing results but seems to disagree with observations of widespread clouds on Jupiter at pressure levels predicted by equilibrium cloud condensation models for ammonia and H2S.  相似文献   

3.
The origin of Jupiter and the Galilean satellite system is examinedin the light of the new data that has been obtained by the NASA Galileo Project. In particular, special attention is given to a theory of satellite origin which was put forward at the start of the Galileo Mission and on the basis of which several predictions have now been proven successful (Prentice, 1996a–c). These predictions concern the chemical composition of Jupiter's atmosphere and the physical structure of the satellites. According to the proposed theory of satellite origin, each of the Galilean satellites formed by chemical condensation and gravitational accumulation of solid grains within a concentricfamily of orbiting gas rings. These rings were cast off equatorially by the rotating proto-Jovian cloud (PJC) which contracted gravitationally to form Jupiter some 4 billion years ago. The PJC formed from the gas and grains left over from the gas ring that had been shed at Jupiter's orbit by the contracting proto-solar cloud (PSC). Supersonic turbulentconvection provides the means for shedding discrete gas rings.The temperatures Tn of the system of gas rings shed by the PSCand PJC vary with their respective mean orbital radii Rn (n = 0, 1, 2, Ϊ ) according as Tn ∝ Rn -0.9. If the planet Mercury condenses at 1640 K, so accounting for the high density ofthat planet via a process of chemical fractionation between iron and silicates, then Tn at Jupiter's orbit is 158 K. Only 35% of the water vapour condenses out. Thus fractionation between rock and ice, together with an enhancement in the abundance of solids relative to gas which takes place through gravitational sedimentation of solids onto the mean orbit of the gas ring, ensures nearly equal proportions of rock and ice in each of Ganymede and Callisto. Io and Europa condense above the H2O ice point and consist solely of hydrated rock (h-rock). The Ganymedan condensate consists of h-rock and H2O ice. For Callisto, NH3 ice makes up ∼5% of the condensate mass next to h-rock (∼50%) and H2O ice (∼45%). Detailed thermal and structural models for each of Europa, Ganymedeand Callisto are constructed on the basis of the above initial bulk chemicalcompositions. For Europa (E), a predicted 2-zone model consisting of a dehydrated rock core of mass 0.912ME and a 150 km thick frozen mantle of salty H2O yields a moment-of-inertiacoefficient which matches the Galileo Orbiter gravity measurement. For Ganymede (G), a 3-zone model possessing an inner core of solid FeS and mass ∼0.116MG, and an outer H2O ice mantle of mass ∼0.502MG is needed to explain the gravity data.Ganymede's native magnetic field was formed by thermoremanent magnetization of Fe3O4. A new Callisto (C) model is proposed consisting of a core of mass 0.826MC containing a uniform mixture of h-rock (60% by mass) and H2O and NH3 ices, and capped by a mantle of pure ice. This model may have the capacity to yield a thin layer of liquid NH3ċ2H2O at the core boundary, in line with Galileo's discovery of an induced magnetic field This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

4.
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   

5.
Detection and measurement of atmospheric water vapor in the deep jovian atmosphere using microwave radiometry has been discussed extensively by Janssen et al. (Janssen, M.A., Hofstadter, M.D., Gulkis, S., Ingersoll, A.P., Allison, M., Bolton, S.J., Levin, S.M., Kamp, L.W. [2005]. Icarus 173 (2), 447-453.) and de Pater et al. (de Pater, I., Deboer, D., Marley, M., Freedman, R., Young, R. [2005]. Icarus 173 (2), 425-447). The NASA Juno mission will include a six-channel microwave radiometer system (MWR) operating in the 1.3-50 cm wavelength range in order to retrieve water vapor abundances from the microwave signature of Jupiter (see, e.g., Matousek, S. [2005]. The Juno new frontiers mission. Tech. Rep. IAC-05-A3.2.A.04, California Institute of Technology). In order to accurately interpret data from such observations, nearly 2000 laboratory measurements of the microwave opacity of H2O vapor in a H2/He atmosphere have been conducted in the 5-21 cm wavelength range (1.4-6 GHz) at pressures from 30 mbars to 101 bars and at temperatures from 330 to 525 K. The mole fraction of H2O (at maximum pressure) ranged from 0.19% to 3.6% with some additional measurements of pure H2O. These results have enabled development of the first model for the opacity of gaseous H2O in a H2/He atmosphere under jovian conditions developed from actual laboratory data. The new model is based on a terrestrial model of Rosenkranz et al. (Rosenkranz, P.W. [1998]. Radio Science 33, 919-928), with substantial modifications to reflect the effects of jovian conditions. The new model for water vapor opacity dramatically outperforms previous models and will provide reliable results for temperatures from 300 to 525 K, at pressures up to 100 bars and at frequencies up to 6 GHz. These results will significantly reduce the uncertainties in the retrieval of jovian atmospheric water vapor abundances from the microwave radiometric measurements from the upcoming NASA Juno mission, as well as provide a clearer understanding of the role deep atmospheric water vapor may play in the decimeter-wavelength spectrum of Saturn.  相似文献   

6.
A theory for the origin and bulk chemical composition of the Galilean satellites is presented — to coincide with the start of the 2-year orbital tour of this satellite system by the Galileo Orbiter. The theory is based on the author's modern Laplacian theory of solar system origin (Prentice 1978a). The nub of the work reported here is that the Jupiter system is indeed a miniature planetary system that formed by much the same physical and chemical processes that were responsible for the condensation of the sun's own family of planets. In particular, a phenomenon of supersonic turbulent convection which I claim caused the proto-solar cloud to rid excess spin angular momentum, by shedding a concentric family of orbiting gas rings at the present planetary orbits, may also have operated with similar effect within the proto-Jovian cloud.Several predictions are made for the bulk chemical composition and physical structure of the icy Galilean satellites which, it is hoped, can be tested by the Galileo Orbiter. The mean density of Callisto is consistent with that of a chemically homogeneous body consisting of about 50% rock, 45% water ice, and 5% ammonia ice, incorporated as the hydrate NH3·H2O. Such a higher-than-solar mass abundance ratio of rock to ice arises naturally within the proto-Jovian cloud since (i) only 34% of the available H2O vapor within the gas ring shed by the proto-solar cloud at Jupiter's orbit was condensed in solid form, and (ii) gravitational sedimentation of solids onto the mean orbit of the proto-solar gas ring leads to an enhancement in the heavy element fraction of the captured primitive Jovian atmosphere. All in all, I predict Jupiter's primitive atmosphere to be enhanced by a factor en 2 in its rock mass fraction (including S) and by a factor 1.3 in its water content, relative to solar abundances. NH3 and CH44 are present in almost solar proportions.Initially, Ganymede consisted of a chemically uniform mixture of rock and water ice in the proportions 0.524 : 0.476. The observed mean density of this satellite, however, lies midway between the mean densities expected for homogeneous and fully differentiated rock/ice bodies. The calculations presented here suggest that this body is about half-differentiated. I predict that the Galileo Orbiter will find the mean axial moment-of-inertia factor of Ganymede to be 0.35 ± 0.01.The circum-Jovian gas ring from which Europa condensed had a temperature of 302 K and a mean orbit gas pressure of 2.8 bar. Initially, this satellite consisted of a uniform mix of hydrated rocks, of which brucite Mg(OH)2 was the principal constituent. The observed mean density of Europa coincides with that expected for this mix, provided that its 9.4% native H2O content is now fractionated from the rock and resides at the satellite surface, forming a frozen mantle some 155 km thick. Regretfully, the mean density of Io cannot be matched by the solid composition reported here. Perhaps this satellite has a molten interior.  相似文献   

7.
Jeremy Bailey 《Icarus》2009,201(2):444-453
The discovery of the near infrared windows into the Venus deep atmosphere has enabled the use of remote sensing techniques to study the composition of the Venus atmosphere below the clouds. In particular, water vapor absorption lines can be observed in a number of the near-infrared windows allowing measurement of the H2O abundance at several different levels in the lower atmosphere. Accurate determination of the abundance requires a good database of spectral line parameters for the H2O absorption lines at the high temperatures (up to ∼700 K) encountered in the Venus deep atmosphere. This paper presents a comparison of a number of H2O line lists that have been, or that could potentially be used, to analyze Venus deep atmosphere water abundances and shows that there are substantial discrepancies between them. For example, the early high-temperature list used by Meadows and Crisp [Meadows, V.S., Crisp, D., 1996. J. Geophys. Res. 101 (E2), 4595-4622] had large systematic errors in line intensities. When these are corrected for using the more recent high-temperature BT2 list of Barber et al. [Barber, R.J., Tennyson, J., Harris, G.J., Tolchenov, R.N., 2006. Mon. Not. R. Astron. Soc. 368, 1087-1094] their value of 45±10 ppm for the water vapor mixing ratio reduces to 27±6 ppm. The HITRAN and GEISA lists used for most other studies of Venus are deficient in “hot” lines that become important in the Venus deep atmosphere and also show evidence of systematic errors in line intensities, particularly for the 8000 to 9500 cm−1 region that includes the 1.18 μm window. Water vapor mixing ratios derived from these lists may also be somewhat overestimated. The BT2 line list is recommended as being the most complete and accurate current representation of the H2O spectrum at Venus temperatures.  相似文献   

8.
P.G.J. Irwin  K. Sihra  F.W. Taylor 《Icarus》2005,176(2):255-271
New measurements of the low-temperature near-infrared absorption of methane (Sihra, 1998, Laboratory measurements of near-infrared methane bands for remote sensing of the jovian atmosphere, Ph.D. thesis, University of Oxford) have been combined with existing, longer path-length, higher-temperature data of Strong et al. (1993, Spectral parameters of self- and hydrogen-broadened methane from 2000 to 9500 cm−1 for remote sounding of the atmosphere of Jupiter, J. Quant. Spectrosc. Radiat. Trans. 50, 309-325) and fitted with band models. The combined data set is found to be more consistent with previous low-temperature methane absorption measurements than that of Strong et al. (1993, J. Quant. Spectrosc. Radiat. Trans. 50, 309-325) but covers the same wider wavelength range and accounts for both self- and hydrogen-broadening conditions. These data have been fitted with k-coefficients in the manner described by Irwin et al. (1996, Calculated k-distribution coefficients for hydrogen- and self-broadened methane in the range 2000-9500 cm−1 from exponential sum fitting to band modelled spectra, J. Geophys. Res. 101, 26,137-26,154) and have been used in multiple-scattering radiative transfer models to assess their impact on our previous estimates of the jovian cloud structure obtained from Galileo Near-Infrared Mapping Spectrometer (NIMS) observations (Irwin et al., 1998, Cloud structure and atmospheric composition of Jupiter retrieved from Galileo NIMS real-time spectra, J. Geophys. Res. 103, 23,001-23,021; Irwin et al., 2001, The origin of belt/zone contrasts in the atmosphere of Jupiter and their correlation with 5-μm opacity, Icarus 149, 397-415; Irwin and Dyudina, 2002, The retrieval of cloud structure maps in the equatorial region of Jupiter using a principal component analysis of Galileo/NIMS data, Icarus 156, 52-63). Although significant differences in methane opacity are found at cooler temperatures, the difference in the optical depth of the atmosphere due to methane is found to diminish rapidly with increasing pressure and temperature and thus has negligible effect on the cloud structure inferred at deeper levels. Hence the main cloud opacity variation is still found to peak at around 1-2 bar using our previous analytical approach, and is thus still in disagreement with Galileo Solid State Imager (SSI) determinations (Banfield et al., 1998, Jupiter's cloud structure from Galileo imaging data, Icarus 135, 230-250; Simon-Miller et al., 2001, Color and the vertical structure in Jupiter's belts, zones and weather systems, Icarus 154, 459-474) which place the main cloud deck near 0.9 bar. Further analysis of our retrievals reveals that this discrepancy is probably due to the different assumptions of the two analyses. Our retrievals use a smooth vertically extended cloud profile while the SSI determinations assume a thin NH3 cloud below an extended haze. When the main opacity in our model is similarly assumed to be due to a thin cloud below an extended haze, we find the main level of cloud opacity variation to be near the 1 bar level—close to that determined by SSI and moderately close to the expected condensation level of ammonia ice of 0.85 bar, assuming that the abundance of ammonia on Jupiter is (7±1)×10−4 (Folkner et al., 1998, Ammonia abundance in Jupiter's atmosphere derived from the attenuation of the Galileo probe's radio signal, J. Geophys. Res. 103, 22,847-22,855; Atreya et al., 1999, A comparison of the atmospheres of Jupiter and Saturn: deep atmospheric composition, cloud structure, vertical mixing, and origin, Planet. Space Sci. 47, 1243-1262). However our data in the 1-2.5 μm range have good height discrimination and our lowest estimate of the cloud base pressure of 1 bar is still too great to be consistent with the most recent estimates of the ammonia abundance of 3.5 × solar. Furthermore the observed limited spatial distribution of ammonia ice absorption features on Jupiter suggests that pure ammonia ice is only present in regions of localised vigorous uplift (Baines et al., 2002, Fresh ammonia ice clouds in Jupiter: spectroscopic identification, spatial distribution, and dynamical implications, Icarus 159, 74-94) and is subsequently rapidly modified in some way which masks its pure absorption features. Hence we conclude that the main cloud deck on Jupiter is unlikely to be composed of pure ammonia ice and instead find that it must be composed of either NH4SH or some other unknown combination of ammonia, water, and hydrogen sulphide and exists at pressures of between 1 and 2 bar.  相似文献   

9.
Using the helium abundance measured by Galileo in the atmosphere of Jupiter and interior models reproducing the observed external gravitational field, we derive new constraints on the composition and structure of the planet. We conclude that, except for helium which must be more abundant in the metallic interior than in the molecular envelope, Jupiter could be homogeneous (no core) or could have a central dense core up to 12M⊕. The mass fraction of heavy elements is less than 7.5 times the solar value in the metallic envelope and between 1 and 7.2 times solar in the molecular envelope. The total amount of elements other than hydrogen and helium in the planet is between 11 and 45M⊕.  相似文献   

10.
Summary. 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 He/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. Received 23 November 1998  相似文献   

11.
Close to 2000 laboratory measurements of the microwave opacity and refractivity of gaseous NH3 in an H2/He atmosphere have been conducted in the 1.1-20 cm wavelength range (1.5-27 GHz) at pressures from 30 mbar to 12 bar and at temperatures from 184 to 450 K. The mole fraction of NH3 ranged from 0.06 to 6% with some additional measurements of pure NH3. The high accuracy of these results have enabled development of a new model for the opacity of NH3 in a H2/He atmosphere under jovian conditions. The model employs the Ben-Reuven lineshape applied to the published inversion line center frequencies and intensities of NH3 (JPL Catalog—[Pickett, H.M., Poynter, R.L., Cohen, E.A., Delitsky, M.L., Pearson, J.C., Müller, H.S.P., 1998. J. Quant. Spectrosc. Radiat. Trans. 60, 883-890]) with empirically-fitted line parameters for H2 and He broadening, and for the self-broadening of some previously unmeasured ammonia inversion lines. The new model for ammonia opacity will provide reliable results for temperatures from 150 to 500 K, at pressures up to 50 bar and at frequencies up to 40 GHz. These results directly impact the retrieval of jovian atmospheric constituent abundances from the Galileo Probe radio signal absorption measurements, from microwave emission measurements conducted with Earth-based radio telescopes and with the future NASA Juno mission, and studies of Saturn's atmosphere conducted with the Cassini Radio Science Experiment and the Cassini RADAR 2.1 cm passive radiometer.  相似文献   

12.
Using standard statistical and thermodynamic procedures, we calculate equilibrium constants for the formation of select, hydrogen-bonded water complexes, namely the water dimer and the cyclic trimer and tetramer, and use them to estimate the atmospheric abundances of these species. We generate water complex altitude profiles (0–30 km) for both a saturated and an unsaturated atmosphere and discuss the dominant factors influencing our results. In our analysis, particular emphasis is given to the significance that water monomer concentrations, complex binding energies, hydrogen-bond energies, and entropy have on the calculated abundance profiles. We examine the importance of enthalpy and entropy at atmospheric temperatures and show how each contributes to our calculated equilibrium constants. By applying a universal 2 °C temperature increase throughout the troposphere and lower stratosphere, we are able to model the effect that global warming would have on (H2O)n abundances in a saturated atmosphere. We also illustrate the effect that this thermal variation would have on entropy, enthalpy, and Kp(T) values. Based on our results, we assess the atmospheric significance of water dimers and cyclic water complexes.  相似文献   

13.
Thomas R. Hanley 《Icarus》2005,177(1):286-290
Laboratory measurements of the microwave opacity of HCl in a CO2 atmosphere have been conducted in the S (13.3 cm), X (3.6 cm), and K (1.4 cm) microwave bands at a pressure of 7.2 bar and at two different mixing ratios. The results are consistent with an opacity model employing the Van Vleck-Weisskopf lineshape applied to the published submillimeter line intensities of HCl (JPL Catalog [Pickett et al., 1998, J. Quant. Spectrosc. Rad. Trans. 60, 883-890]) and empirically fitted with a modeled parameter for CO2 broadening. Based on the deep atmospheric abundance of HCl inferred from near-infrared measurements [Dalton et al., 2000, Bull. Am. Astron. Soc. 32, 1120], the resulting modeled HCl opacity is constrained to have a small effect on the overall microwave absorption spectrum of Venus, but can be used in developing a more accurate radiative transfer model.  相似文献   

14.
The seasonal evolution of the H2O snow in the Martian polar caps and the dynamics of water vapor in the Martian atmosphere are studied. It is concluded that the variations of the H2O mass in the polar caps of Mars are determined by the soil thermal regime in the polar regions of the planet. The atmosphere affects water condensation and evaporation in the polar caps mainly by transferring water between the polar caps. The stability of the system implies the presence of a source of water vapor that compensates for the removal of water from the atmosphere due to permanent vapor condensation in the polar residual caps. The evaporation of the water ice that is present in the surface soil layers in the polar regions of the planet is considered as such a source. The annual growth of the water-ice mass in the residual polar caps is estimated. The latitudinal pattern of the seasonal distribution of water vapor in the atmosphere is obtained for the stable regime.Translated from Astronomicheskii Vestnik, Vol. 38, No. 6, 2004, pp. 497–503.Original Russian Text Copyright © 2004 by Aleshin.  相似文献   

15.
A multi-wavelength radio frequency observation of Venus was performed on April 5, 1996, with the Very Large Array to investigate potential variations in the vertical and horizontal distribution of temperature and the sulfur compounds sulfur dioxide (SO2) and sulfuric acid vapor (H2SO4(g)) in the atmosphere of the planet. Brightness temperature maps were produced which feature significantly darkened polar regions compared to the brighter low-latitude regions at both observed frequencies. This is the first time such polar features have been seen unambiguously in radio wavelength observations of Venus. The limb-darkening displayed in the maps helps to constrain the vertical profile of H2SO4(g), temperature, and to some degree SO2. The maps were interpreted by applying a retrieval algorithm to produce vertical profiles of temperature and abundance of H2SO4(g) given an assumed sub-cloud abundance of SO2. The results indicate a substantially higher abundance of H2SO4(g) at high latitudes (above 45°) than in the low-latitude regions. The retrieved temperature profiles are up to 25 K warmer than the profile obtained by the Pioneer Venus sounder probe at altitudes below 40 km (depending on location and assumed SO2 abundance). For 150 ppm of SO2, it is more consistent with the temperature profile obtained by Mariner 5, extrapolated to the surface via a dry adiabat. The profiles obtained for H2SO4(g) at high latitudes are consistent with those derived from the Magellan radio occultation experiments, peaking at around 8 ppm at an altitude of 46 km and decaying rapidly away from that altitude. At low latitudes, no significant H2SO4(g) is observed, regardless of the assumed SO2 content. This is well below that measured by Mariner 10 (Lipa and Tyler 1979, Icarus39, 192-208), which peaked at ∼14 ppm near 47 km. Our results favor ≤100 ppm of SO2 at low latitudes and ≤50 ppm in polar regions. The low-latitude value is statistically consistent with the results of Bézard et al. (1983, Geophs. Res. Lett.20, 1587-1590), who found that a sub-cloud SO2 abundance of 130±40 ppm best matched their observations in the near-IR. The retrieved temperature profile and higher abundance of H2SO4(g) in polar regions are consistent with a strong equatorial-to-polar, cloud-level flow due to a Hadley cell in the atmosphere of Venus.  相似文献   

16.
Observations of the 1.10- and 1.18-μm nightside windows by the SPICAV-IR instrument aboard Venus Express were analyzed to characterize the various sources of gaseous opacity and determine the H2O mole fraction in the lower atmosphere of Venus. We showed that the line profile model of Afanasenko and Rodin (Afanasenko, T.S., Rodin, A.V. [2007]. Astron. Lett. 33, 203–210) underestimates the CO2 absorption in the high-wavelength wing of the 1.18-μm window and we derived an empirical lineshape that matches this wing well. An additional continuum opacity is required to reproduce the variation of the 1.10- and 1.18-μm radiances with surface elevation as observed by the VIRTIS-M instrument aboard Venus Express. A constant absorption coefficient of 0.7 ± 0.2 × 10−9 cm−1 am−2 best reproduces the observed variation. We compared spectra calculated with different CO2 and H2O line lists. We found that the CDSD line list lacks the 5ν1 + ν3 series of CO2 bands, which provide significant opacity in Venus’ deep atmosphere, and we have constructed a composite line list that best reproduces the observations. We also showed for the first time that HDO brings significant absorption at 1140–1190 nm. Using the best representation of the atmospheric opacity we could reach, we retrieved a water vapor mole fraction of ppmv, pertaining to the altitude range 5–25 km. Combined with previous measurements in the 1.74- and 2.3-μm windows, this result provides strong evidence for a uniform H2O profile below 40 km, in agreement with chemical models.  相似文献   

17.
R.J Sault  Chermelle Engel 《Icarus》2004,168(2):336-343
We present a technique for creating a longitude-resolved image of Jupiter's thermal radio emission. The technique has been applied to VLA data taken on 25 January 1996 at a wavelength of 2 cm. A comparison with infrared data shows a good correlation between radio hot spots and the 5 μm hot spots seen on IRTF images. The brightest spot on the radio image is most likely the hot spot through which the Galileo probe entered Jupiter's atmosphere. We derived the ammonia abundance (= volume mixing ratio) in the hot spot, which is ∼3×10−5, about half that seen in longitude-averaged images of the NEB, or less than 1/3 of the longitude-averaged ammonia abundance in the EZ. This low ammonia abundance probably extends down to at least the 4 bar level.  相似文献   

18.
伽利略探测器对木星深部的大气测量，进一步增加了木星大气的平均带状交替快速环流是由其深部大气运动产生的可能性。由于木星高速自转，所以此带状流的基本动力学特征是地转流，即主要动力学平衡是科里奥利力和压力。基于近两维和非轴对称地转慢波的非线性相互作用，描述了一个新的带状交替环流的分析理论，并给出了地转波动的一个显函数关系分析表达式，以及它对应于弱非线性问题的首阶解。对考虑非线性效应的高阶解问题，推导出了一个运动方向交替的快速环流的分析表达式。也对该理论在木星和其他行星的大气动力学研究方面作了讨论。  相似文献   

19.
Measurements by the Galileo probe in Jupiter's deep atmosphere support the possibility that the mean zonal multiple-jet flows in Jupiter's atmosphere are deep rooted. As a consequence of Jupiter's high rotation rate, the primary dynamics of the zonal flows must be geostrophic, i.e., the dynamic balance is largely between the Coriolis and pressure forces. This paper describes a new analytical theory for the generation of zonal multiple-jet flows on the basis of the nonlinear interaction of slowly traveling, nearly two-dimensional and non-axisymmetric geostrophic waves. An explicit analytical expression for the geostrophic waves is obtained as the leading-order solution of the weakly nonlinear problem. In the high-order problem taking into account of nonlinear effects, an analytical expression for an alternating multiple-jet flow is derived. Implications of the theory for Jupiter and other planets are discussed.  相似文献   

20.
In situ measurements of the Venus atmosphere, made by the entry probes Venera 4, 5, 6, and 7, and data from the Mariner 5 flyby, have provided essentially new and reliable information and have powerfully contributed to our understanding of the nearest planet. The abundances of the principal atmospheric constituents and the temperature and pressure profiles down to the Venus surface were obtained for the first time. It was shown that the atmosphere is composed primarily of CO2 and that N2 (if any) and H2O are relatively minor admixtures. In the region of the Venera 7 landing, the temperature and pressure at the Venus surface were established as equal to 747 ± 20°K and 90 ± 15 kgcm−2. Space vehicles have also provided limited but quite important information on the physical properties of the Venus upper atmosphere and ionosphere, and on the interaction of the planet with the interplanetary environment. The main characteristics of the Venus atmosphere are discussed here with emphasis on the Venera results, including instrumentation, data processing, and altitude profiles.  相似文献   

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