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Even though many missions have explored the Venus atmospheric circulation, its instantaneous state is poorly characterized. In situ measurements vertically sampling the atmosphere exist for limited locations and dates, while remote sensing observations provide only global averages of winds at altitudes of the clouds: 47, 60, and 70 km. We present a three‐dimensional global view of Venus's atmospheric circulation from data obtained in June 2007 by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) and Venus Express spacecrafts, together with ground‐based observations. Winds and temperatures were measured for heights 47–110 km from multiwavelength images and spectra covering 40°N–80°S and local times 12 h–21 h. Dayside westward winds exhibit day‐to‐day changes, with maximum speeds ranging 97–143 m/s and peaking at variable altitudes within 75–90 km, while on the nightside these peak below cloud tops at ∼60 km. Our results support past reports of strong variability of the westward zonal superrotation in the transition region, and good agreement is found above the clouds with results from the Laboratoire de Météorologie Dynamique (LMD) Venus general circulation model. The atmosphere of the Earth or Mars globally rotates with a speed similar to the rotation of the planet (approximately 24 h). The rotation of Venus is of about 243 days, much slower than the Earth, but when scientists measured the winds by tracking the clouds of Venus, they discovered that the atmosphere rotates 60 times faster! No one has explained yet what originates this “superrotation,” and we do not know well what happens either above or below the clouds. The technique of “Doppler shift” has been used to measure winds above the clouds, but results are “chaotic” and different to interpret. Thanks to a worldwide collaboration in June 2007 between NASA (MESSENGER), ESA (Venus Express), and many observatories (VLT in Chile, JCMT in Hawaii, HHSMT in Arizona, or IRAM in Spain), the authors combined the different data to obtain, for the first time, the instantaneous 3‐D structure of the winds on Venus at the clouds and also above, very important for new Venus models to start “forecasts” of the Venus weather with “data assimilation”. We also discovered that the superrotation seems unexpectedly different on the night of Venus and that it varies its altitude depending on the day. The 3‐D quasi‐simultaneous winds on Venus's day and night from combining space and ground observationsWe detect and quantify day‐to‐night and temporal wind changes between altitudes 50 and 120 kmComparison between wind data and GCM predictions indicates good agreement, but deviations occur at 60–70 km in nighttime

Context. Pluto possesses a thin atmosphere, primarily composed of nitrogen, in which the detection of methane has been reported.

Context. Small body (12929) 1999 TZ1is listed by the Minor Planet Center (MPC) as a Centaur. However, its location close to the Lagrangian point L5 of Jupiter is typical of a Trojan object with large inclination.

The Odin satellite, thanks to the versatility of its receiver and spectrometer system, is well suited for the study of wide planetary submillimetre lines. In June and November 2003, the H2O line at 557 GHz was observed in the Mars atmosphere over a total bandwidth of 4 GHz. The wings of the line are detected up to the nearby continuum, which provides constraints on the disc-averaged vertical thermal profile and atmospheric water mixing ratio. In parallel, a sensitive search for the O2line at 487 GHz was undertaken in June. This search was negative with a 3 σupper limit of 4% on the absorption line depth, which is twice the expected signal. This observation, however, provides information on the continuum of Mars. In November the CO J(5-4) and the H$_2^{18}$O lines were also detected in parallel and provide additional constraints on the temperature profile and mixing ratios. Surface water mixing ratios of $2{-}3\times10^{-4}$are inferred, corresponding to column densities in the range of 10-15 precipitable μm.

Heterodyne observations of Neptune have provided a measurement of the CO(2–1) line profile with a total bandpass of almost 8 GHz and a resolution of 4 MHz. The lineshape indicates that the CO mole fraction in Neptune's atmosphere is not uniform, but increases by a factor of ~2 from the troposphere/lower stratosphere (0.5 ppm at $p>20$mbar) to the upper stratosphere (1 ppm at $p<20$mbar). This indicates the existence of both external and internal sources of CO. The equivalent flux associated with the external source is ~$1\times10^8$cm-2s-1. We propose that the stratospheric CO results from a large (2 km) cometary impact that occurred ~200 years ago, although there remains problems with this hypothesis.

We report on physical properties of the bright Trans-Neptunian Object 2003 TX300based on a large set of observations taken in different wavelength ranges. Broad band CCD observations aimed at studying the short-term rotational variability show a low amplitude periodic signal of $7.89 \pm 0.03$h. We cannot yet determine whether the lightcurve is single-peaked (i.e. the rotation period would be 7.89 h) or double-peaked (i.e. the actual spin period would be 15.78 h). From a sinusoidal fit, the peak to peak amplitude of the brightness changes is $0.09 \pm 0.08$mag. If the brightness changes are due to irregular shape, this amplitude implies a minimum axial ratio of 1.09. BVRIphotometry indicates similar colors as other large Kuiper Belt members, with $B-V = 0.64 \pm 0.04$, $V-R = 0.40 \pm 0.07$, and $R-I = 0.22 \pm 0.05$. Thermal observations at 250 GHz (1.2 mm) result in no confident detection of the body, with a measured flux of $0.22 \pm 0.51$mJy. Combining all the data and using the same thermophysical model as in Lellouch et al. ([CITE]) we find (at a 3-σconfidence level) a lower limit for the geometric albedo ($p_v>0.06$) and an upper limit for the size of this object ($D<$1110 km). A more relaxed 2-σconfidence level implies a diameter $D< 907$km and an albedo $p_v> 0.08$, which is significantly higher than the typical 0.04 cometary value and also higher than that of Varuna.

The spectrum of Uranus has been recorded in Oct.–Nov. 2002, between 4.6 and 5.0 μm, using the ISAAC imaging spectrometer at the VLT-UT1 (ANTU) 8-m telescope of ESO. The spectral resolving power was 1500. In addition to a few strong H3+emission lines, the spectrum of Uranus distinctly shows the emission lines of the CO(1–0) band from R7 to P8. The relative intensity distribution of the observed CO emission is not compatible with a thermal distribution, for any value of the rotational temperature. The most likely emission mechanism is fluorescence, and a good fit is obtained assuming a constant CO mixing ratio of $3\times 10^{-8}$at the tropopause and above. The tropospheric continuum of Uranus is also detected beween 4.7 and 5.0 μm. The observed continuum can be fitted assuming reflected sunlight above a cloud level at 3.1 bars, presumably attributed to H2S. Upper limits of $2\times 10^{-8}$and $1\times 10^{-6}$are inferred for the CO and PH3tropospheric mixing ratios above this level. The low CO tropospheric upper limit might suggest that the CO vertical distribution is not uniform.

We report on coordinated thermal and optical measurements of trans-Neptunian object (20 000)Varuna obtained in January–February 2002, respectively from the IRAM 30-m and IAA 1.5 m telescopes. The optical data show a lightcurve with a period of $3.176 \pm 0.010$hr, a mean Vmagnitude of $20.37 \pm 0.08$and a $0.42 \pm 0.01$magnitude amplitude. They also tentatively indicate that the lightcurve is asymmetric and double-peaked. The thermal observations indicate a $1.12\pm 0.41$mJy flux, averaged over the object's rotation. Combining the two datasets, we infer that Varuna has a mean 1060$^{+180}_{-220}$km diameter and a mean 0.038$^{+0.022}_{-0.010}$Vgeometric albedo, in general agreement with an earlier determination using the same technique.

We have searched for several rotational lines of CO in the Pluto-Charon system, Centaurs (Chiron, Pholus, Nessus, Asbolus, Chariklo and 1998 SG35) and Kuiper Belt objects (1994 TB, 1996 TL66, 1996 TO66, 1996 TP66 and 1998 WH4). The observations were performed with the 30 m telescope of the Institut de Radioastronomie Millimétrique for Pluto/Charon, and with the James Clerk Maxwell Telescope and Caltech Submillimeter Observatory for Centaurs and Kuiper Belt objects. A tentative 4.5-σ$J(2{-}1)$CO line is present in the Pluto/Charon spectrum, which requires further confirmation. Assuming that Charon does not contribute to the CO emission, an upper limit of 1.2% and 7% is obtained for the CO/N2mixing ratio in Pluto's atmosphere, using the atmospheric thermal structure derived from the Stansberry et al. (1994, Icarus 111, 503) and Strobel et al. (1996, Icarus 120, 266) models, respectively. These upper limits are more constraining (by more than a factor of 6) than the upper limits reported by Young et al. (2001, Icarus, in press) from near-IR spectroscopy. None of the Centaurs or Kuiper Belt objects (KBO) were detected in CO. The CO production rate upper limit obtained for Chiron ($3{-}5 \times 10^{27}$mol s-1) over 1998-2000 years is a factor of 10 lower than the CO production rate derived from the marginal CO detection obtained in June 1995 by Womack & Stern ([CITE], Astron. Vestnik 33, 216), using same modelling of CO emission. Upper limits obtained for other Centaurs are typically ~1028mol s-1, and between 1 and $5 \times 10^{28}$mol s-1for the best observed KBOs. The comparison between these upper limits and the CO outgassing rates of comet C/1995 O1 (Hale-Bopp) measured at large distances from the Sun shows that Centaurs and KBOs underwent significant CO-devolatilization since their formation.

Observations with the Short Wavelength Spectrometer (SWS) onboard the Infrared Space Observatory (ISO) are used to determine the D/H ratio in Jupiter's and Saturn's atmospheres. The D/H ratio is measured independently in hydrogen (i.e. from the HD/H2ratio) and methane (from CH3D/CH4). Observations of the HD R(2) and R(3) rotational lines at 37.7 and 28.5 μm, of the H2S(0) and S(1) quadrupolar lines at 17.1 and 28.2 μm, of the methane $\nu_4$band at 7.7 μm, and of the CH3D $\nu_6$band at 8.6 μm are analyzed jointly, allowing a retrieval of thermal profiles and molecular abundances. On each planet, the D/H determinations from H2and CH4give consistent results, but the accuracy is not sufficient to precisely determine the enrichment factor of D/H in methane. Combining these determinations, we obtain the following values for the D/H ratio in hydrogen: (D/H)$_{\rm H_2}= (2.25\pm 0.35) 10^{-5}$in Jupiter and $(1.70^{+0.75}_{-0.45}) 10^{-5}$on Saturn. These values are consistent with and somewhat more accurate than most earlier values. Comparing with inferences of protosolar D/H from solar wind measurements, it is confirmed that Jupiter is a reliable indicator of the protosolar D/H ratio. The protosolar deuterium abundance inferred from the jovian value, ($2.1 \pm 0.4) 10^{-5}$, indicates a minor decrease of the D/H ratio, over the last 4.55 Gyr, in the part of the Galaxy where the Solar System was formed. Although the error bars overlap, most measurements, including ours, may point to a slightly smaller D/H ratio in Saturn's atmosphere than in Jupiter's, a surprising result which needs confirmation.

Context. In 2003, the Sun and the Earth passed through both the equatorial plane of Jupiter and therefore the orbital planes of its main satellites. Aims. During this period, mutual eclipses and occultations were observed and we present the data collected.Methods. Light curves of mutual eclipses and occultations were recorded by the observers of the international campaign PHEMU03 organized by the Institut de m?canique c?leste, Paris, France. Results. We completed 377?observations of 118?mutual events from 42?sites and the corresponding data are presented in this paper. For each observation, information about the telescope, receptor, site, and observational conditions are provided.Conclusions. This paper gathers all data and indicates a first estimate of its precision. This catalogue of these rare events should constitute an improved basis for accurate astrometric data useful in the development of dynamical models.

Aims. We have recorded high spectral resolution spectra and derived precise atmospheric temperature profiles and wind velocities in the atmosphere of Mars. We have compared observations of the planetary mean thermal profile and mesospheric wind velocities on the disk, obtained with our millimetric observations of CO?rotational lines, to predictions from the Laboratoire de M?t?orologie Dynamique (LMD) Mars General Circulation Model, as provided through the Mars Climate Database (MCD) numerical tool.Methods. We observed the atmosphere of Mars at CO(1-0) and CO(2-1) wavelengths with the IRAM 30-m antenna in June?2001 and November?2005. We retrieved the mean thermal profile of the planet from high and low spectral resolution data with an inversion method detailed here. High spectral resolution spectra were used to derive mesospheric wind velocities on the planetary disk. We also report here the use of 13CO(2-1)?line core shifts to measure wind velocities at 40?km.Results. Neither the Mars Year 24 (MY24) nor the Dust Storm scenario from the Mars Climate Database (MCD) provides satisfactory fits to the 2001 and 2005 data when retrieving the thermal profiles. The Warm scenario only provides good fits for altitudes lower than 30?km. The atmosphere is warmer than predicted up to 60?km and then becomes colder. Dust loading could be the reason for this mismatch. The MCD?MY24?scenario predicts a thermal inversion layer between 40 and 60?km, which is not retrieved from the high spectral resolution data. Our results are generally in agreement with other observations from 10 to 40?km in altitude, but our results obtained from the high spectral resolution spectra differ in the 40-70?km layer, where the instruments are the most sensitive. The wind velocities we retrieve from our 12CO?observations confirm MCD?predictions for 2001 and 2005. Velocities obtained from 13CO?observations are consistent with MCD? predictions in 2001, but are lower than predicted in 2005.

Aims. We observed Saturn and Uranus at CO?millimetric line wavelengths in order to better constrain the origin of CO in the atmospheres of these planets. CO?sources can be either of internal or of external origin. Methods. We recorded broad multi-band spectra of Saturn and Uranus at the frequencies of the J?= 1?? 0 and J?= 2?? 1?CO?lines. Results. As we do not detect any CO line in the spectra, we derive new upper limits of the abundance of CO in the atmospheres of Saturn and Uranus. The value we obtain for Saturn (6.3?? 10-8, restricted to the stratosphere) is larger than the value of the CO?mixing ratio in the external origin model used. New observations with higher sensitivity and/or longer observing time should enable us to determine the CO?external source strength. The upper limit we derive on Uranus is slightly lower (2.7?? 10-8, restricted to the stratosphere) than the value derived from an early observation of CO on Uranus, at infrared wavelength. As the fluorescence model used then did not take scattering effects into account, we suggest that the value could be overestimated.

Aims. In spite of considerable progress in the last two decades, Io's?atmosphere remains poorly understood. The goal of this work is to improve our understanding of its spatial distribution, temperature and dynamics.Methods. We present millimeter observations of Io's surface and SO2?atmosphere at 1.4?mm obtained with the IRAM Plateau de Bure Interferometer in January-February?2005. With a synthesized beam of 0.5?1.5?, these observations resolve Io's ~1.0??disk in the longitudinal / local time direction, and sample the leading and trailing hemispheres of Io.Results. The measured continuum total flux and visibilities show that continuum radiation originates from a depth of at least 1?cm in Io's?subsurface. On both the leading and trailing sides, emission in the SO2216.643?GHz line appears spatially narrower than the continuum, and suggests that the atmosphere covers ~80% of the surface on the leading side and ~60% on the trailing. On the leading side, disk-resolved spectra yield Doppler shift measurements, indicating a beam-integrated limb-to-limb velocity difference of 330?? 100?m/s in the prograde direction. Such a flow allows an improved fit of disk-averaged SO2spectra, but its origin remains to be understood. Mean gas temperatures are in the range 130-180?K, in agreement with estimates from IR?measurements, and with a tendency for higher trailing vs leading side gas temperatures. On the basis of realistic plume models, we find that the contribution of isolated volcanic plumes to the SO2?emission is small.

We report on repeated bolometric observations of the Pluto–Charon system at 1.2 mm with the IRAM 30-m telescope. These observations indicate at most small (∼1–2 mJy) variations of the millimeter-wave emission of Pluto with orbital longitude, suggesting that the dark regions of Pluto have a millimeter emissivity of ∼0.6–0.7.

Line positions and intensities belonging to the vibrational system 2ν2/ν4of ammonia 14NH3are measured and analyzed between 1200 and 2200 cm−1in order to improve the molecular database. For this, laboratory spectra are obtained at 0.006 and 0.011 cm−1unapodized resolution and with 4% precisions for the intensities using Fourier transform spectrometers located at the Kitt Peak National Observatory and the Jet Propulsion Laboratory. The observed data contain transitions of the ν4fundamental band near 1626.276(1) and 1627.375(2) cm−1(for sand ainversion upper states, respectively) and the 2ν2overtone band near 1597.470(3) and 1882.179(5) cm−1(for sand ainversion states, respectively). A total of 2345 lines with J′ ≤ 15 is assigned from which 2114 line positions with J′ ≤ 15 are fitted using an effective rotation–inversion–rotation Hamiltonian to achieve an rms of 0.003 cm−1with 57 molecular parameters. Over 1200 intensity measurements are modeled to ±4.7% using 16 terms of the dipole moment expansion. A dyad model is used in order to model all the interactions expected within the 2ν2/ν4system. The bandstrengths of 2ν2(s← a), 2ν2(a← s), and ν4(s← sand a← a) are estimated to be 6.68(24), 0.201(5), and 116(3) cm−2atm−1, respectively, at 296 K. The prediction generated by this study is available for planetary studies.

We report on repeated far-infrared photometric observations of the Pluto–Charon system conducted in 1997 with the Infrared Space Observatory (ISO). These observations have led to the first detection of the system at 150 and 200 μm and to the first clear detection of its thermal lightcurve at 60 μm (and more marginally at 100 μm). They definitely prove that Pluto's surface is not isothermal. The thermal lightcurve is, as expected, roughly anticorrelated with the visible lightcurve, but not exactly. The data are fit by physical models including Charon and three separate units on Pluto, respectively dominated by (1) N2-ice (2) CH4-ice, and (3) tholins. These models are constructed in accordance with information from visible imaging and lightcurves, visible spectroscopy and infrared spectroscopy, and considerations on the thermal balance of N2 and CH4, and they include a thermophysical description of subsurface conduction and infrared beaming. Charon's contribution, which cannot be separated from Pluto's in the observations, is assumed to be independent of longitude and equivalent to that of a ∼52 K body. The main implications are that Pluto's surface in units 2 and 3 has a thermal inertia Γ=(1.5–10)×104 erg cm−2 s−1/2 K−1, comparable to that of other icy satellites, and relatively high bolometric emissivities (not lower than 0.5 and most likely 0.8–1). Diurnal temperature variations must be significant, with maximum dayside temperatures in the range 54–63 K. The value of thermal inertia may be indicative of porosity in the top centimeters of Pluto's surface. The observations further confirm that the far-IR brightness temperatures, though somewhat smaller than indicated by IRAS, are higher than in the millimeter/submillimeter range. Extending the models to longer wavelengths suggests that a low radio emissivity, as opposed to a mixing of temperatures or a subsurface sounding effect, is the correct explanation. Finally, in spite of large error bars, the 150-μm fluxes indicated by ISO seem unexpectedly high given the spectral properties of ices in the far-IR. These, and the expected lightcurves of the Pluto–Charon system at λ=15–60 μm should be priority measurements for SIRTF.

A series of far infrared (FIR) spectra of Mars between 43 and 196 μm was taken with the Long Wavelength Spectrometer (LWS) on board the European Space Agency's Infrared Space Observatory (ISO). Analysis of these medium-resolution data reveals a rotational modulation of the disk-averaged FIR brightness temperature. The observed variability of ±1.5% in the LWS wavelength range compares favorably with the predictions of a thermophysical model of the martian surface. A surface emissivity of ∼0.90 gives good agreement between the measured and the modeled brightness temperatures and leads to an improved estimate of the LWS photometric calibration uncertainty.

Infrared spectra of Mars were taken with the two complementary spectrometers onboard the European Space Agency's Infrared Space Observatory (ISO), in both moderate- and high-resolution mode. From the strengths of the observed water lines we derived information about the vertical distribution of water vapor and on the emissivity of the dust/surface system in the infrared. Assuming atmospheric and surface temperatures derived from the European Martian Climate Database with a slight adjustment to the observed 15-μm CO2 band, the ISO data are consistent with an H2O mixing ratio of (3±1)×10−4 at the surface, a saturation level at 13±2 km, and a total column density of 12±3.5 pr-μm. The mean disk emissivity is found to be close to 1.0 at 6 μm and 0.92±0.02 at 40 μm. At longer wavelengths the emissivity decreases from a value of 0.97±0.03 at 50μm to 0.92±0.03 at 180 μm.

The 183-GHz water vapor line was tentatively detected on Mars in January 1991, with the IRAM 30-m millimeter antenna, under extremely dry atmospheric conditions. The measurement refers to the whole disk. The spectral line, although marginally detected, can be fit with a constant H₂O mixing ratio of 1.0 × 10^-5, which corresponds to a water abundance of 1 pr-µm; in any case, an upper lime of 3 pr-µan is inferred. This value is comparable to the very small abundances measured by Clancy (1992, Icarus 100, 48-59) 5 five weeks before our observation and seems to imply both seasonal and long-term variations in the martian water cycle. Copyright 1995, 1999 Academic Press

We have observed Jupiter on July 24, 25, 26 and 27, 1994, in thermal infrared, using the French National 10 micron array camera “C10µ”, mounted on the Canada‐France‐Hawaii 3.6 meter telescope. The observations were made using both broad‐band and narrowband filters, as well as a Circular Variable Filter (CVF). Two observing programs were scheduled, one concerning atmospheric observations and the other one focusing on seismological observations (Lognonné et al., 1994). We present here preliminary results concerning the atmospheric program. The main result is that persistent brightness temperature enhancements still exist several days after the impacts at several wavelengths, corresponding to a long term perturbation associated to the impact sites.

The possible existence of stable warming at middle altitudes in the martian atmosphere was first examined by J. R. Barnes (J. Geophys. Res.95, 1401, 1990) in one-dimensional modeling of the effect of breaking gravity waves on the general circulation. This work was motivated by infrared observations of D. Deming, M. J. Mumma, F. Espenak, T. Kostius, and D. Zipoy (Icarus66, 366, 1986) which suggested temperatures far from radiative equilibrium above polar regions at solstice. New observational evidence was obtained from heterodyne measurements of the J= 2-1 12CO and 13CO transitions made during the 1988 opposition. At this date, corresponding to southern summer solstice, these lines were mapped as a function of the position on the martian disk with the IRAM 30-m telescope. Wind velocities near 50 km altitude and vertical thermal profiles were derived from the Doppler shift and the line profiles, respectively, at various locations on Mars. The northern (winter) hemisphere profiles indicate the presence of a warm layer in the 40-60-km altitude range, with a relative warming of ≈5 K compared to smoothly decreasing temperature profiles such as those found in the southern hemisphere. This may be interpreted in terms of a temperature inversion in the northern middle atmosphere. Such a phenomenon may be similar to the stable inversion layers observed in the terrestrial mesosphere, which are believed to be a response to the gravity wave activity. We show that a zonally averaged model of the martian middle atmosphere, using the parametrization of gravity waves effects propounded by R. S. Lindzen (J. Geophys. Res.86, 9707, 1981). is able to produce both a plausible zonal wind field consistent with the measurements of E. Lellouch, J. J. Goldstein, S. W. Bougher, G. Paubert and J. Rosenqvist (Astrophys, J.383, 401, 1991) and a thermal field in good agreement with the observations. The 2-D modeling further indicates that weak equatorial thermal inversions may occur, due to the penetration of the summer hemisphere retrograde jet into the winter hemisphere.

We report observations of Titan covering the 1.075-, 1.28-, 1.6-, and 2.0-μm windows which show variations with the orbital phase, implying variability of the satellite's geometric albedo, as found earlier by other authors. The observations cover the region 4400 to 9600 cm-1and were taken in June 1991, August 1993, and September 1994, using the Fourier transform spectrometer at the CFH Telescope (Hawaii). The resolving power was 10000, 1000, and 300 for the 1991, 1993, and 1994 spectra, respectively. The data sets cover Titan's Greatest Western Elongation and opposite Conjunctions. We find Titan's geometric albedo to be about the same (0.29) at 1.28 and 1.075 μm. (On the other hand, our observations of Uranus show the 1.28-μm albedo to be lower by 30% than that in the 1.075μm window.) The geometric albedos in the 1.6- and 2.0-μm methane windows on Titan are clearly lower (0.20 and 0.16, respectively). At the four wavelengths, a noticeable decrease in geometric albedo is observed near Greatest Western Elongation with respect to Inferior and Superior Conjunctions. The sum of the existing Titan data point to a bright leading side and a darker trailing one, with a maximum brightness near 120° (±20°) orbital longitude and a minimum near 230° (±20°). Despite important uncertainties in the value of the CH4absorption coefficients in the window regions, modeling Titan's observed albedos strongly suggests the existence of a surface material with a comparable albedo at 1.075 and 1.28 μm (0.4-0.5) but much darker at 1.6 and 2.0 μm (about 0.2). Titan's surface spectrum appears consistent with that of Hyperion and we suggest that this behavior may be due to the dominant presence of water ice on Titan's surface. The inhomogeneity of the surface implies that some other material (e.g., hydrocarbon lakes) is mixed with water ice in variable proportions.

An analysis of thermal profiles and dynamics over a wide range of latitudes for the venusian atmosphere between 70 and 90 km is presented based on high spatial resolution infrared spectra of the night side obtained by the near infrared mapping spectrometer (NIMS) experiment during the Galileo-Venus encounter in February 1990. Using the 4.3-µm CO₂ absorption band, the temperature profile is retrieved in the 75- to 91-km altitude region over a latitudinal range of -59° to + 64°. Compared to earlier observations from the Pioneer Venus mission, the temperature at 91 km is about 10 K higher and between 74 and 83 km about 3.6 K colder. An equator to pole warming at constant pressure levels is found and implications for the zonal wind profiles are drawn under the assumption that the atmosphere is in cyclostrophic balance in the region of 70 to 90 km. The results are in correspondence with direct wind measurements from ground-based observations at 95 km and 105 km altitude. Copyright 1995, 1999 Academic Press

C/1995 O1 (Hale-Bopp) has been observed on a regular basis since August 1995 at millimetre and submillimetre wavelengths using IRAM, JCMT, CSO and SEST radio telescopes. The production rates of eight molecular species (CO, HCN, CH3OH, H2CO,H2S, CS, CH3CN,HNC) have been monitored as a function of heliocentric distance(rhfrom 7 AU pre-perihelion to 4 AU post-perihelion. As comet Hale-Bopp approached and receded from the Sun, these species displayed different behaviours. Far from the Sun, the most volatile species were found in general relatively more abundant in the coma. In comparison to other species, HNC, H2CO and CS showed a much steeper increase of the production rate with decreasing rh. Less than 1.5 AU from the Sun, the relative abundances were fairly stable and approached those found in other comets near 1 AU.

The occultation of a star by Neptune on 20 August 1985 was observed at 2.2 µm wavelength with telescopes at the European Southern Observatory (ESO) and the Cerro Tololo Inter-American Observatory (CTIO). The detection of a ‘central flash’ midway between immersion and emersion has allowed the determination of Neptune's oblateness, ε, and the atmospheric extinction at 2.2 µm, which is related to the stratospheric methane mixing ratio. We find ε = (2.08+0.19−0.18) × 10−2and, assuming a stratospheric temperature of 120 K, infer a value of 0.6% (with an uncertainty of a factor of 10) for the methane mixing ratio (CH4/H2) at 0.3 mbar. The latter value may indicate supersaturation of methane in Neptune's stratosphere.

The 183.310-GHz water vapor transition has been observed in the Venus atmosphere for the first time. The detection was made in January 1991, using the 30-m IRAM radiotelescope. A spectrum of Saturn, recorded during the same night, was used to remove the contribution due to terrestrial mesospheric water. Using the depth and the FWHM of the observed absorption line, we derive a water mixing ratio of 1.0 (+ 1.0, -0.5) ppm above the clouds, and a temperature of 140 (±10) K at the level z = 95 km (P = 0.06 mb). In July 1993, we reobserved the HDO transition at 225.987 GHz, which we first detected in August 1990 (T. Encrenaz et al. 1991, Astron. Astrophys. 246, L63-L66). The new set of data was obtained at the Caltech Submillimeter Observatory (CSO), with improved signal-to-noise and spectral resolution with respect to previous measurements. From the 1993 data we derive a water mixing ratio of 7.0 (+5.0, -4.0) ppm above the clouds, and a temperature higher than 145 K at the z = 95-km level. The water abundance is derived assuming a deuterium enrichment factor of 120 with respect to the terrestrial value (C. de Bergh et al. 1991, Science 251, 547-549). If the deuterium enrichment factor is close to 160, as measured by G. L. Bjoraker et al. (1992, Bull. Am. Astron. Soc. 24, 995-995), the difference between the H₂O measurements is reduced, but the data might still suggest some possible fluctuation in the water vapor content above the clouds between 1991 and 1993. Copyright 1995, 1999 Academic Press

Spectra of comet C/1995 O1 (Hale-Bopp) were obtained with the Infrared Space Observatory (ISO) at medium resolution with the grating spectrometer in the photometer (PHT-S) and/or at high resolution with the short wavelength spectrometer (SWS) and long wavelength spectrometer (LWS) in April 1996 (Crovisier et al., 1996), September–October 1996 (Crovisier et al., 1997a, b) and December 1997, at distances from the Sun of 4.6, 2.9 and 3.9 AU, respectively. For the first time, high-resolution spectra of a comet covering the entire 2.4 to 200 μm spectral range were obtained.

In this paper, we investigate the opportunities provided by the James Webb Space Telescope(JWST) for significant scientific advances in the study of Solar System bodies and rings using stellar occultations. The strengths and weaknesses of the stellar occultation technique are evaluated in light of JWST's unique capabilities. We identify several possible JWSToccultation events by minor bodies and rings and evaluate their potential scientific value. These predictions depend critically on accurate a priori knowledge of the orbit of JWSTnear the Sun-Earth Lagrange point 2 (L2). We also explore the possibility of serendipitous stellar occultations by very small minor bodies as a byproduct of other JWSTobserving programs. Finally, to optimize the potential scientific return of stellar occultation observations, we identify several characteristics of JWST's orbit and instrumentation that should be taken into account during JWST's development.

We investigate the composition of Titan’s stratosphere from high-resolution submillimetric observations performed with the SPIRE instrument on the Herschel satellite. From the flux density spectrum measured in the 20 − 52 cm-1interval at an apodized resolution of 0.08 cm-1, we determine the stratospheric abundances of CH4, CO, HCN, as well as the isotopic ratios 12C/13C = 87  ±  6 in CO and 96  ±  13 in HCN, 14N/15N = 76  ±  6, and 16O/18O = 380  ±  60. The last of these results is the first documented measurement of Titan’s 16O/18O ratio in CO, with a value 24% lower than the terrestrial ratio.

We report on the first identification of hydrogen isocyanide (HNC) in Titan’s atmosphere, from observations using the HIFI instrument on the Herschel⋆Space Observatory. An emission line from the HNC J= 6 → 5 rotational transition at 543.897 GHz was measured in Titan on June 14 and December 31, 2010. Radiative transfer modeling indicates that the bulk of HNC is located above 400 km, with a column density in the range (0.6−1.5) × 1013cm-2, but the observations cannot establish its vertical profile. In particular HNC could be restricted to the upper thermosphere (~1000 km), in which case its local abundance relative to HCN could be as high as  ~0.3. HNC is probably formed mostly at ionospheric levels (950–1150 km) from dissociative recombination of HCNH+and possibly other heavier nitrile ions. Ionospheric loss of HNC occurs by protonation with XH+ions. Additional formation (e.g. from N(4S) +3CH2) and loss routes (e.g. from isomerization to HCN) in the neutral atmosphere remain to be investigated.

Cryovolcanic activity near the south pole of Saturn’s moon Enceladus produces plumes of H2O-dominated gases and ice particles, which escape and populate a torus-shaped cloud. Using submillimeter spectroscopy with Herschel, we report the direct detection of the Enceladus water vapor torus in four rotational lines of water at 557, 987, 1113, and 1670 GHz, and probe its physical conditions and structure. We determine line-of-sight H2O column densities of  ~4 × 1013cm-2near the equatorial plane, with a  ~50 000 km vertical scale height. The water torus appears to be rotationally cold (e.g. an excitation temperature of 16 K is measured for the 1113 GHz line) but dynamically excited, with non-Keplerian dispersion velocities of  ~2 km s-1, and appears to be largely shaped by molecular collisions. From estimates of the influx rates of torus material into Saturn and Titan, we infer that Enceladus’ activity is likely to be the ultimate source of water in the upper atmosphere of Saturn, but not in Titan’s.

Aims.The goal is to determine the composition of Pluto’s atmosphere and to constrain the nature of surface-atmosphere interactions.Methods.We perform high-resolution spectroscopic observations in the 2.33–2.36 μm range, using CRIRES at the VLT.Results.We obtain (i) the first detection of gaseous methane in this spectral range, through lines of the ν3+ ν4and ν1+ ν4bands (ii) strong evidence (6-σconfidence) for gaseous CO in Pluto. For an isothermal atmosphere at 90 K, the CH4and CO column densities are 0.75 and 0.07 cm-am, within factors of 2 and 3, respectively. Using a physically-based thermal structure model of Pluto’s atmosphere also satisfying constraints from stellar occultations, we infer CH4and CO mixing ratios \hbox{$q_{\rm CH_4}= 0.6^{+0.6}_{-0.3}$}% (consistent with results from the 1.66 μm range) and \hbox{$q_{\rm CO} = 0.5^{+1}_{-0.25}\,\times\,10^{-3}$}. The CO atmospheric abundance is consistent with its surface abundance. As for Triton, it is probably controlled by a thin, CO-rich, detailed balancing layer resulting from seasonal transport and/or atmospheric escape.

Context.Little is known about the physical properties of cometary nuclei. Measuring the thermal emission of a nucleus is one of the few means of deriving its size, independently of its albedo, and constraining some of its thermal properties. This emission is difficult to detect from Earth but space telescopes, such as th Infrared Space Observatory, Spitzer Space Telescope, and Herschel Space Observatory, allow reliable measurements to be made in the infrared and the sub-millimetre domains.

We report on the initial analysis of Herschel/HIFI carbon monoxide (CO) observations of the Martian atmosphere performed between 11 and 16 April 2010. We selected the (7–6) rotational transitions of the isotopes 13CO at 771 GHz and C18O and 768 GHz in order to retrieve the mean vertical profile of temperature and the mean volume mixing ratio of carbon monoxide. The derived temperature profile agrees within less than 5 K with general circulation model (GCM) predictions up to an altitude of 45 km, however, show about 12–15 K lower values at 60 km. The CO mixing ratio was determined as 980 ±150 ppm, in agreement with the 900 ppm derived from Herschel/SPIRE observations in November 2009.

The high spectral resolution and sensitivity of Herschel/HIFI allows for the detection of multiple rotational water lines and accurate determinations of water production rates in comets. In this Letter we present HIFI observations of the fundamental 110–101(557 GHz) ortho and 111–00(1113 GHz) para rotational transitions of water in comet 81P/Wild 2 acquired in February 2010. We mapped the extent of the water line emission with five point scans. Line profiles are computed using excitation models which include excitation by collisions with electrons and neutrals and solar infrared radiation. We derive a mean water production rate of 1.0× 1028molecules s-1at a heliocentric distance of 1.61 AU about 20 days before perihelion, in agreement with production rates measured from the ground using observations of the 18-cm OH lines. Furthermore, we constrain the electron density profile and gas kinetic temperature, and estimate the coma expansion velocity by fitting the water line shapes.

We report on an initial analysis of Herschel/HIFI observations of hydrogen chloride (HCl), hydrogen peroxide (H2O2), and molecular oxygen (O2) in the Martian atmosphere performed on 13 and 16 April 2010 (Ls~ 77°). We derived a constant volume mixing ratio of 1400 ±120 ppm for O2and determined upper limits of 200 ppt for HCl and 2 ppb for H2O2. Radiative transfer model calculations indicate that the vertical profile of O2may not be constant. Photochemical models determine the lowest values of H2O2to be around Ls~ 75° but overestimate the volume mixing ratio compared to our measurements.

The high spectral resolution and sensitivity of Herschel/HIFI allows for the detection of multiple rotational water lines and accurate determinations of water production rates in comets. In this Letter we present HIFI observations of the fundamental 110–101(557 GHz) ortho and 111–00(1113 GHz) para rotational transitions of water in comet 81P/Wild 2 acquired in February 2010. We mapped the extent of the water line emission with five point scans. Line profiles are computed using excitation models which include excitation by collisions with electrons and neutrals and solar infrared radiation. We derive a mean water production rate of 1.0× 1028molecules s-1at a heliocentric distance of 1.61 AU about 20 days before perihelion, in agreement with production rates measured from the ground using observations of the 18-cm OH lines. Furthermore, we constrain the electron density profile and gas kinetic temperature, and estimate the coma expansion velocity by fitting the water line shapes.

We report on an initial analysis of Herschel/HIFI observations of hydrogen chloride (HCl), hydrogen peroxide (H2O2), and molecular oxygen (O2) in the Martian atmosphere performed on 13 and 16 April 2010 (Ls~ $77\degr$). We derived a constant volume mixing ratio of 1400 ±120 ppm for O2and determined upper limits of 200 ppt for HCl and 2 ppb for H2O2. Radiative transfer model calculations indicate that the vertical profile of O2may not be constant. Photochemical models determine the lowest values of H2O2to be around Ls~ $75\degr$but overestimate the volume mixing ratio compared to our measurements.

We report on the initial analysis of Herschel/HIFI carbon monoxide (CO) observations of the Martian atmosphere performed between 11 and 16 April 2010. We selected the (7–6) rotational transitions of the isotopes 13CO at 771 GHz and C18O and 768 GHz in order to retrieve the mean vertical profile of temperature and the mean volume mixing ratio of carbon monoxide. The derived temperature profile agrees within less than 5 K with general circulation model (GCM) predictions up to an altitude of 45 km, however, show about 12–15 K lower values at 60 km. The CO mixing ratio was determined as 980 ±150 ppm, in agreement with the 900 ppm derived from Herschel/SPIRE observations in November 2009.