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1.
We present latitudinally-resolved high-resolution (R = 37,000) pole-to-pole spectra of Jupiter in various narrow longitudinal ranges, in spectral intervals covering roughly half of the spectral range 2.86-3.53 μm. We have analyzed the data with the aid of synthetic spectra generated from a model jovian atmosphere that included lines of CH4, CH3D, NH3, C2H2, C2H6, PH3, and HCN, as well as clouds and haze. Numerous spectral features of many of these molecular species are present and are individually identified for the first time, as are many lines of and a few unidentified spectral features. In both polar regions the 2.86-3.10-μm continuum is more than 10 times weaker than in spectra at lower latitudes, implying that in this wavelength range the single-scattering albedos of polar haze particles are very low. In contrast, the 3.24-3.53 μm the weak polar and equatorial continua are of comparable intensity. We derive vertical distributions of NH3, C2H2 and C2H6, and find that the mixing ratios of NH3 and C2H6 show little variation between equatorial and polar regions. However, the mixing ratios of C2H2 in the northern and southern polar regions are ∼6 and ∼3 times, respectively, less than those in the equatorial regions. The derived mixing ratio curves of C2H2 and C2H6 extend up to the 10−6 bar level, a significantly higher altitude than most previous results in the literature. Further ground-based observations covering other longitudes are needed to test if these mixing ratios are representative values for the equatorial and polar regions. 相似文献
2.
The atmospheric transmission window at 2.7 μm in Jupiter's atmosphere was observed at a spectral resolution of 0.1 cm?1 from the Kuiper Airborne Observatory. From analysis of the CH4 abundance (～80m-am) and the H2O abundance (<0.0125cm-am) it was determined that the penetration depth of solar flux at 2.7 μm is near the base of the NH3 cloud layer. The upper limit to H2O at 2.7 μm and other recent results suggest that photolytic reactions in Jupiter's lower troposphere may not be as significant as was previously thought. The search for H2S in Jupiter's atmosphere yielded an upper limit of ～0.1cm-am. The corresponding limit to the elemental abundance ratio [S]/[H] was ～1.7 × 10?8, about 10?3 times the solar value. Upon modeling the abundance and distribution of H2S in Jupiter's atmosphere it was concluded that, contrary to expectations, sulfur-bearing chromophores are not present in significant amounts in Jupiter's visible clouds. Rather, it appears that most of Jupiter's sulfur is locked up as NH4SH in a lower cloud layer. Alternatively, the global abundance of sulfur in Jupiter may be significantly depleted. 相似文献
3.
The visible (0.3 to 1.03 μm) spectral reflectances of H2O, NH3, H2S, and NH4HS frosts and mixtures of these frosts and their uv irradiated products have been measured. These spectra are compared with the spectra of the Galilean satellites of Jupiter, Saturn's rings and Saturn's satellites to place limits on their surface composition. 相似文献
4.
L.M. Trafton 《Icarus》1975,24(4):443-453
Detailed analysis of the R(5) manifold of Titan's 3ν3 CH4 band confirms that the column abundance of Titan's spectroscopically visible atmosphere is greater than 1.6 kmamagats. This agrees with the value estimated from the strength of Titan's 3ν3 CH4Q branch and is at least 25 times the value for the column abundance of Mars' atmosphere. Moreover, the enhanced strength of the weaker CH4 lines in Titan's spectrum relative to Saturn's spectrum suggests that CH4 constitutes a significant fraction of this bulk.Recently discovered strong, unidentified absorptions in Titan's spectrum at 1.05–1.06 μm have been compared with laboratory spectra of a number of gases including CH4, C2H4, C2H6, and C3H8 with negative results. These comparisons, however, have not excluded the possibility that these features arise from a very large quantity of CH4 or from an isotope of CH4. The fundamental transition of the responsible molecule may affect the interpretation of Titan's 8–14 μm spectrum since its wavelength may lie in this window. Comparison with Uranus' spectrum suggests that the visible abundance of this molecule in Titan's atmosphere may be much greater than in Uranus' relatively clear, deep atmosphere.Spectra of features at λ8150.7 and λ8272.7 attributed possibly to H2 have been obtained at high resolution also during the apparitions of 1971, 1972, and 1973. These are presented for comparison with the results of the 1970 apparition. The existence of the λ8150.7 feature is established definitively but further observations are needed to establish whether the λ8272.7 feature exists beyond doubt. 相似文献
5.
Laser-induced plasmas in various gas mixtures were used to simulate lightning in other planetary atmospheres. This method of simulation has the advantage of producing short-duration, high-temperature plasmas free from electrode contamination. The laser-induced plasma discharges in air are shown to accurately simulate terrestrial lightning and can be expected to simulate lightning spectra in other planetary atmospheres. Spectra from 240 to 880 nm are presented for simulated lightning in the atmospheres of Venus, Earth, Jupiter, and Titan. The spectra of lightning on the other giant planets are expected to be similar to that of Jupiter because the atmospheres of these planets are composed mainly of hydrogen and helium. The spectra of Venus and Titan show substantial amounts of radiation due to the presence of carbon atoms and ions and show CN Violet radiation. Although small amounts of CH4 and NH3 are present in the Jovian atmosphere, only emission from hydrogen and helium is observed. Most differences in the spectra can be understood in terms of the elemental ratios of the gas mixtures. Consequently, observations of the spectra of lightning on other planets should provide in situ estimates of the atmospheric and aerosol composition in the cloud layers in which lightning is occuring. In particular, the detection of inert gases such as helium should be possible and the relative abundance of these gases compared to major constituents might be determined. 相似文献
6.
Spectral observations of Saturn from the far infrared spectrometer aboard the Cassini spacecraft [Flasar, F.M., et al., 2005. Temperatures, winds, and composition in the Saturnian system. Science 307, 1247-1251] have revealed that the C/H ratio in the planet is in fact about twice higher than previously derived from ground based observations and in agreement with the C/H value derived from Voyager IRIS by Courtin et al. [1984. The composition of Saturn's atmosphere at northern temperate latitudes from Voyager IRIS spectra - NH3, PH3, C2H2, C2H6, CH3D, CH4, and the Saturnian D/H isotopic ratio. Astrophys. J. 287, 899-916]. The implications of this measurement are reanalyzed in the present report on the basis that volatiles observed in cometary atmospheres, namely CO2, CH4, NH3 and H2S may have been trapped as solids in the feeding zone of the planet. CH4 and H2S may have been in the form of clathrate hydrates while CO2 presumably condensed in the cooling solar nebula. Carbon may also have been incorporated in organics. Conditions of temperature and pressure ease the hydratation of NH3. Such icy grains were included in planetesimals which subsequently collapsed into the hydrogen envelope of the planet, then resulting in C, N and S enrichments with respect to the solar abundance. Our calculations are consistent, within error bars, with observed elemental abundances on Saturn provided that the carbon trapped in planetesimals was mainly in the form of CH4 clathrate and CO2 ice (and maybe as organics) while nitrogen was in the form of NH3 hydrate. Our approach has implications on the possible pattern of noble gases in Saturn, since we predict that contrary to what is observed in Jupiter, Ar and Kr should be in solar abundance while Xe might be strongly oversolar. The only way to verify this scenario is to send a probe making in situ mass spectrometer measurements. Our scenario also predicts that the 14N/15N ratio should be somewhat smaller in Saturn than measured in Jupiter by Galileo. 相似文献
7.
Laboratory transmission IR spectra of relatively thick films (up to 500 m) of mixed H2O and SO2 ices were measured at several temperatures between 10 and 130 K in the range 5000-450 cm–1. In addition to the strong features due to crystalline SO2 the spectra reveal bands at 3668 cm–1, 3634 cm–1 (with some structure) and 3300 cm–1 which are identified with H2O in SO2 environment. Also, there is no overlap between any of the H2O bands with the 3584 cm–1 band of SO2 at any temperature in the above range. The implication of this result is that H2O, if present on Io, must be far less than 1 part in 105 SO2. 相似文献
8.
The formation of methylamine (CH3NH2) in the upper troposphere and lower stratosphere of Jupiter is investigated. Translationally hot hydrogen atoms are produced in the photolysis of ammonia, phosphine, and acetylene which react with methane to produce methyl (CH3) radicals; the latter recombine with NH2 to form CH3NH2. Also, methane is catalytically dissociated to CH3 + H by the species C2 and C2H produced in the photolysis of acetylene. It is shown that the combined production of CH3NH2 and subsequent photolysis to HCN is unlikely to account for the HCN observed near Jupiter's tropopause. Recombination of NH2 and C2H5N followed by photolysis to HCN is the preferred path. Production of C2H6 by these two processes is negligible in comparison to the downward flux of C2H6 from the Lyman α photolysis region of CH4. An upper limit column density on CH3PH2 is estimated to be ～1013 cm?2 as compared to 1015 cm?2 for CH3NH2. Hot H atoms account for a negligible fraction of the total ortho-para conversion by the reaction H + H2 相似文献
9.
Jupiter exhibits bright H+3 auroral arcs at 3-4 microns that cool the hot (>1000 K) ionosphere above the ∼10−7 bar level through the infrared bands of this trace constituent. Below the 10−7 bar level significant cooling proceeds through infrared active bands of CH4, C2H2, and C2H6. We report the discovery of 3-micron line emission from these hydrocarbon species in spectra of the jovian south polar region obtained on April 18 and 20, 2006 (UT) with CGS4 on the United Kingdom Infrared Telescope. Estimated cooling rates through these molecules are 7.5×10−3, 1.4×10−3, and , respectively, for a total nearly half that of H+3. We derive a temperature of 450 ± 50 K in the 10−7-10−5 bar region from the C2H2 lines. 相似文献
10.
V.G. Teifel 《Icarus》1983,53(3):389-398
Modeling of the geometric albedo of Uranus in and near prominent methane absorption bands between 0.5 and 0.9 μm indicates that the visible atmosphere probably consists of a thin aerosol haze layer (τscat ? 0.3?0.5; ωH ? 0.95) above an optically thick, semi-infinite Rayleigh scattering atmosphere. A significant depletion of methane gas above the haze layer is indicated. The mixing ratio of methane in the lower atmosphere is consistent with a value of CH4/H2 ? 3 × 10?3, comparable to those derived for Jupiter and Saturn. 相似文献
11.
New thermal profiles of Jupiter are retrieved from recent far infrared spectral measurements and for H2 mixing ratios varying from 0.8 to 0.94. The effective temperature corresponding to the inferred thermal profile is 123.15 ± 0.35°K. Far-infrared brightness temperature spectra computed from these profiles are compared to experimental data including measurements made at high spectral resolution in the NH3ν2 band at 10 μm and in NH3 pure rotational bands between 40 and 110 μm. It is found that a strong depletion of NH3 does occur in the Jovian stratosphere and that ammonia seems to be undersaturated in the upper troposphere. 相似文献
12.
The spectral window of Jupiter at 3 μm is analyzed and compared with previously published spectra. The two components of the spectrum, the thermal and the solar reflected contributions, are calculated at low resolution (30 cm?1) between 3300 and 3800 cm?1 for preparing the interpretation of the Galileo Near Infrared Mapping Spectrometer experiment. The calculations yield to the following conclusions: (1) NH3 is the main absorber between 3300 and 3600 cm?1 for both the thermal spectrum and the solar reflected spectrum; H2O appears only in the thermal component above 3600 cm?1. (2) The thermal component can be seen only on the dark side of Jupiter; the atmosphere is sounded down to temperature levels of about 210°K. (3) The solar reflected component can be modelized by a reflecting layer between 135 and 140°K with an albedo of 0.3; high spatial resolution maps of Jupiter at 3 μm should give access to the NH3 spatial distribution on Jupiter. 相似文献
13.
A. Léger J. M. Mariotti B. Mennesson M. Ollivier J. L. Puget D. Rouan J. Schneider 《Astrophysics and Space Science》1996,241(1):135-146
Angel and co-workers have proposed to detect exoplanets around nearby stars in the infrared (6–17 m) and to analyze their spectra, searching for H2O, CO2, CH4, NH3, and O3 spectral features. The presence or absence of CO2 would indicate either a strong similarity or difference with Solar telluric planet atmospheres. Water would indicate a habitable planet, and O3 would reveal significant photosynthesis activity, due to the presence of carbon chemistry based life. Like these authors, we suggest an infrared nulling interferometer pointing to the star and working as a coronograph. Our main contribution is to propose an observatory made of four to five 1-meter class telescopes observing from about 4 to 5 AU to avoid the Solar Zodiacal Light (ZL) background at 10m instead of four 8-meter ones observing from the Earth vicinity. This allows the mission to be feasible in thenear future. The concept, named DARWIN, is under consideration by the European Space Agency for its Horizon 2000 Plus program. 相似文献
14.
Tobias Owen 《Planetary and Space Science》1982,30(8):833-838
The discovery that Titan had an atmosphere was made by the identification of methane in the satellite's spectrum in 1944. But the abundance of this gas and the identification of other major constituents required the 1980 encounter by the Voyager 1 spacecraft. In the intervening years, traces of C2H2, C2H4, C2H6 and CH3D had been posited to interpret emission bands in Titan's i.r. spectrum. The Voyager Infra-red Spectrometer confirmed that these gases were present and added seven more. The atmosphere is now known to be composed primarily of molecular nitrogen. But the derived mean molecular weight suggests the presence of a significant amount of some heavier gas, most probably argon. It is shown that this argon must be primordial, and that one can understand the evolution of Titan's atmosphere in terms of degassing of a mixed hydrate dominated by CH4, N2 and 36Ar. This model satisfactorily explains the absence of neon and makes no special requirements on the satellite's surface temperature. 相似文献
15.
A model of the atmospheric structure of Uranus is presented which differs from previous types of models in two important respects: (1) The CH4/H2 ratio is sufficiently large that CH4 is saturated to large depths in the Uranian atmosphere. (2) The internal energy flux is small compared with that due to solar heating. Because of the small internal flux, the thermal flux decreases rapidly with depth and the atmosphere is radiative to large optical depths. A CH4 droplet cloud forms where the atmosphere finally becomes convective due to the internal flux. The model is shown to be in reasonable agreement with published observations of the H2 quadrupole 3-0 and 4-0 bands, the visible (4000–6000 Å) CH4 bands, and the infrared emission spectrum. 相似文献
16.
Spectra of Jupiter recorded in the 1900- to 2300-cm?1 range at the IRTF in Hawaii, July 1982, provide tentative evidence for variability of the Jovian atmosphere between zones and belts. It is concluded from analysis of the ν1and ν3 bands of PH3 that there is a possible enhancement of the PH3/H2 ratio in the belts when compared to the zones. There is an apparent reduction of the PH3 abundance between the IRIS Voyager 1 determinations and these spectra, implying temporal or spatial variability of PH3 on Jupiter. Interpretation of this variability in the troposphere could involve both dynamical and thermochemical processes. 相似文献
17.
L. Trafton 《Icarus》1985,63(3):374-405
We report the results of monitoring Saturn's H2 quadrupole and CH4 band absorptions outside of the equatorial zone over one-half of Saturn's year. This interval covers most of the perihelion half of Saturn's elliptical orbit, which happens to be approximately bounded by the equinoxes. Marked long-term changes occur in the CH4 absorption accompanied by weakly opposite changes in the H2 absorption. Around the 1980 equinox, the H2 and CH4 absorptions in the northern hemisphere appear to be discontinuous with those in the southern hemisphere. This discontinuity and the temporal variation of the absorptions are evidence for seasonal changes. The absorption variations can be attributed to a variable haze in Saturn's troposphere, responding to changes in temperature and insolation through the processes of sublimation and freezing. Condensed or frozen CH4 is very unlikely to contribute any haze. The temporal variation of the absorption in the strong CH4 bands at south temperate latitudes is consistent with a theoretically expected phase lag of 60° between the tropopause temperature and the seasonally variable insolation. We model the vertical haze distribution of Saturn's south temperature latitudes during 1971–1977 in terms of a distribution having a particle scale height equal to a fraction of the atmospheric scale height. The results are a CH4/H2 mixing ratio of (4.2 ± 0.4) × 10?3, a haze particle albedo of , and a range of variation in the particle to gas scale-height ratio of 0.6 ± 0.2. The haze was lowest near the time of maximum temperature. We also report spatial measurements of the absorption in the 6450 Å NH3 band made annually since the 1980 equinox. A 20 ± 4% increase in the NH3 absorption at south temperate latitudes has occurred since 1973–1976 and the NH3 absorption at high northern latitudes has increased during spring. Increasing insolation, and the resulting net sublimation of NH3 crystals, is probably the cause. Significant long-term changes apparently extend to the deepest visible parts of Saturn's atmosphere. An apparently anomalous ortho-para H2 ratio in 1978 suggests that the southern temperate latitudes experienced an unusual upwelling during that time. This may have signaled a rise in the radiative-convective boundary from deep levels following maximum tropospheric temperature and the associated maximum radiative stability. This would be further evidence that the deep, visible atmosphere is governed by processes such as dynamics and the thermodynamics of phase changes, which have response times much shorter than the radiative time constant. 相似文献
18.
Spectroscopic observations in the spectral region 6000–6600 » of major belts and zones of Jupiter have been carried out at Calar Alto Observatory (Spain) during the 1987 opposition, in support to the International Jupiter Watch Program. More than a hundred long-slit, medium resolution spectra have been taken at the coudé focus of the 1.52 m telescope. The longitudinal and latitudinal distribution of the equivalent widths of the methane and ammonia absorption bands at 6190 » and 6450 » have been investigated. Unlike the CH4-6190 » band, the longitudinal distribution in the NH3-6450 » band shows asymmetries in some of the Jovian regions analyzed, being the absorption greater at West than at East limbs. These results are interpreted in terms of inhomogeneous scattering models by the simultaneous variation of the NH3 cloud optical thickness and its altitude level. The north-south scans show little latitudinal dependence on absorption in both methane and ammonia bands, although some relationship could be established between the absorption and relative continuum reflectivity variation.
Also at Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Campus Universitario Fuentenueva, Granada, Spain. 相似文献
Resumen Se presentan los resultados obtenidos de las observaciones espectroscópicas de las principales zonas y cinturones de Júpiter realizadas durante la oposición de 1987 como una contribución al International Jupiter Watch Program. Las observaciones fueron llevadas a cabo haciendo uso del foco coudé del telescopio de 1.52 m del observatorio hispanoalemán de Calar Alto (España), habiéndose obtenido algo más de cien espectros, de resolución media, en la región espectral de 6000–6600 ». Se exponen los resultados de las anchuras equivalentes de las bandas de absorción del metano en 6190 » y del amoniaco en 6450 », estudiándose, al mismo tiempo, la distribución tanto longitudinal como latitudinal de las mismas. Mientras que los resultados para la banda del metano presentan un comportamiento simétrico en todas las regiones analizadas, las anchuras equivalentes para la banda NH3-6450 » presentan un comportamiento asimétrico en algunas regiones del planeta, con una mayor absorción hacia el limbo del oeste que hacia el del este. Los resultados son interpretados en base a un modelo de scattering no homogéneo, variando, simultáneamente, el espesor óptico y la altitud de la nube de amoniaco. Los espectros tomados en la dirección norte-sur, aunque presentan una dependencia latitudinal pequeña en la absorción de las bandas mencionadas, sugieren una relación entre la absorción y las variaciones de reflectividad en el continuo.
Also at Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Campus Universitario Fuentenueva, Granada, Spain. 相似文献
19.
We have elaborated an evolutionary turbulent model of the subnebula of Saturn derived from that of Dubrulle (1993, Icarus106, 59-76) for the solar nebula, which is valid for a geometrically thin disk. We demonstrate that if carbon and nitrogen were in the form of CO and N2, respectively, in the early subnebula, these molecules were not subsequently converted into CH4 and NH3 during the evolution of the disk, contrary to the current scenario initially proposed by Prinn and Fegley (1981, Astrophys. J., 249, 308-317). However, if the early subnebula contained some CH4 and NH3, these gases were not subsequently converted into CO and N2. We argue that Titan must have been formed from planetesimals migrating from the outer part of the subnebula to the present orbit of the satellite. These planetesimals were relics of those embedded in the feeding zone of Saturn prior to the completion of the planet and contained hydrates of NH3 and clathrate hydrates of CH4. It is shown that, for plausible abundances of CH4 and NH3 in the solar nebula at 10 AU, the masses of methane and nitrogen trapped in Titan were higher than the estimate of masses of these components in the primitive atmosphere of the satellite. If our scenario is valid and if our turbulent model properly describes the structure and the evolution of the actual subnebula of Saturn, the Xe/C ratio should be six times higher in Titan's atmosphere today than in the Sun, while the current scenario would probably result in a quasi solar Xe/C ratio. The mass spectrometer and gas chromatograph instrument aboard the Huygens Titan probe of the Cassini mission has the capability of measuring this ratio in 2004, thus permitting us to discriminate between the current scenario and the one proposed in this report. 相似文献
20.
A spectrum of Jupiter between 6000 and 12 000 cm? at high resolution (0.05 cm?) was recorded with a Michelson interferometer at Palomar Mountain in October 1974. An analysis of the R branch of the 3ν3CH4 band with the reflecting-layer model, taking into account the H2 absorption which occurs in the same spectral range, leads to a Lorentzian half-width of 0.09 ± 0.02 cm?1, a rotational temperature of 175 ± 10° K, and a CH4 abundance of order 52m atm. Five lines of the 13CH43ν3 band have been identified; a comparison with new laboratory spectra indicates that the 13CH4/12CH4 ratio in the Jupiter atmosphere is close to the terrestrial ratio. 相似文献