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Planetary rings are observed not only around giant planets1, but also around small bodies such as the Centaur Chariklo2and the dwarf planet Haumea3. Up to now, all known dense rings were located close enough to their parent bodies, being inside the Roche limit, where tidal forces prevent material with reasonable densities from aggregating into a satellite. Here we report observations of an inhomogeneous ring around the trans-Neptunian body (50000) Quaoar. This trans-Neptunian object has an estimated radius4of 555 km and possesses a roughly 80-km satellite5(Weywot) that orbits at 24 Quaoar radii6,7. The detected ring orbits at 7.4 radii from the central body, which is well outside Quaoar’s classical Roche limit, thus indicating that this limit does not always determine where ring material can survive. Our local collisional simulations show that elastic collisions, based on laboratory experiments8, can maintain a ring far away from the body. Moreover, Quaoar’s ring orbits close to the 1/3 spin–orbit resonance9with Quaoar, a property shared by Chariklo’s2,10,11and Haumea’s3rings, suggesting that this resonance plays a key role in ring confinement for small bodies.

In comets, iron and nickel are found in refractory dust particles or in metallic and sulfide grains1. So far, no iron- or nickel-bearing molecules have been observed in the gaseous coma of comets2. Iron and a few other heavy atoms, such as copper and cobalt, have been observed only in two exceptional objects: the Great Comet of 18823and, almost a century later, C/1965 S1 (Ikeya–Seki)4–9. These sungrazing comets approached the Sun so closely that refractory materials sublimated, and their relative abundance of nickel to iron was similar to that of the Sun and meteorites7. More recently, the presence of iron vapour was inferred from the properties of a faint tail in comet C/2006 P1 (McNaught) at perihelion10, but neither iron nor nickel was reported in the gaseous coma of comet 67P/Churyumov–Gerasimenko by the in situ Rosetta mission11. Here we report that neutral Fe iand Ni iemission lines are ubiquitous in cometary atmospheres, even far from the Sun, as revealed by high-resolution ultraviolet–optical spectra of a large sample of comets of various compositions and dynamical origins. The abundances of both species appear to be of the same order of magnitude, contrasting the typical Solar System abundance ratio.

Our aim is to determine the isotopic ratios 12C/13C and 14N/15N in a variety of comets and link these measurements to the formation and evolution of the solar system. The 12C/13C and 14N/15N isotopic ratios are measured for the CN radical by means of high-resolution optical spectra of the Rbranch of the B-X (0, 0) violet band. 23 comets from different dynamical classes have been observed, sometimes at various heliocentric and nucleocentric distances, in order to estimate possible variations of the isotopic ratios in parent molecules. The 12C/13C and 14N/15N isotopic ratios in CN are remarkably constant (average values of, respectively, 91.0 ±3.6 and 147.8 ±5.7) within our measurement errors, for all comets whatever their origin or heliocentric distance. While the carbon isotopic ratio does agree with the terrestrial value (89), the nitrogen ratio is a factor of two lower than the terrestrial value (272), indicating a fractionation in the early solar system, or in the protosolar nebula, common to all the comets of our sample. This points towards a common origin of the comets independently of their birthplaces, and a relationship between HCN and CN.

The 16OH/18OH and OD/OH isotope ratios are measured in the Oort-Cloud comet C/2002 T7 (LINEAR) through ground-based observations of the OH $A\,^{2}\Sigma^{+} - X\,^{2}\Pi_{i}$ultraviolet bands at 3063 Å (0, 0) and 3121 Å (1, 1) obtained with the Very Large Telescope (VLT) feeding the Ultraviolet-Visual Echelle Spectrograph (UVES). From the 16OH/18OH ratio, we find 16O/18O = $425 \pm 55$, equal within the uncertainties to the terrestrial value and to the ratio measured in other comets, although marginally smaller. We also estimate OD/OH from which we derive ${\rm D/H} = 2.5 \pm 0.7\times 10^{-4}$in water. This value is compatible with the water D/H ratios evaluated in other comets and is marginally higher than the terrestrial value.

Aims.We present observations of CN emission and the scattered solar light on cometary dust particles around the impact time of the Deep Space spacecraft (NASA) into the nucleus of comet 9P/Tempel 1. The purpose of the observations was to compare post-impact activity to the conditions pre-impact to search for new spectral emission lines after impact, to quantify the increase in gas activity due to the impact and to study the long-term activity changes.

Aims.It is unclear whether chemically peculiar stars of the upper main sequence represent a class completely distinct from normal A-type stars, or whether there exists a continuous transition from the normal to the most peculiar late F- to early B-type stars. A systematic abundance analysis of open cluster early-type stars would help to relate the observed differences of the chemical abundances of the photospheres to other stellar characteristics, without being concerned by possible different original chemical composition. Furthermore, if a continuous transition region from the very peculiar to the so called normal A–F stars exists, it should be possible to detect objects with mild peculiarities.

The 12C14N/12C15N and 12C14N/13C14N isotopic ratios are determined for the first time in a Jupiter-family comet, 88P/1981 Q1 Howell, and in the chemically peculiar Oort Cloud comet C/1999 S4 (LINEAR). By comparing these measurements to previous ones derived for six other Oort Cloud comets (including one of Halley-type), we find that both the carbon and nitrogen isotopic ratios are constant within the uncertainties. The mean values are 12C/13C $\simeq$90 and 14N/15N $\simeq145$for the eight comets. These results strengthen the view that CN radicals originate from refractory organics formed in the protosolar molecular cloud and subsequently incorporated in comets.

Accurate relative abundances have been obtained for carbon, oxygen, sodium, aluminium, silicon, and calcium in a sample of mildly metal-poor stars. This analysis complements a previous study carried out by Jehin et al. ([CITE], A&A, 341, 241), which provided the basis for the EASE scenario. This scenario postulates that field metal-poor stars were born in self-enriched proto-globular cluster clouds. By further investigating the correlations between the different α-element abundances, we propose a modified scenario for the formation of intermediate metallicity stars, in which the stars exhibiting lower than average α/Fe abundance ratios would form in low mass clouds, unable to sustain the formation of very massive stars ($M \ga 30~M_\odot$).
Moreover, the carbon-to-iron ratio is found to decrease as one climbs the so-called Population IIb branch, i.e. when the s-element abundance increases. In the framework of the EASE scenario, we interpret this anticorrelation between the carbon and the s-element abundances as a signature of a hot bottom burningprocess in the metal-poor AGB stars which expelled the matter subsequently accreted by our Population IIb stars.

For the first time the possible presence of radial gradients of magnetic fields in the atmospheres of three magnetic Ap stars has been critically examined by measurements of the mean magnetic field modulus from spectral lines resolved into magnetically split components lying on the different sides of the Balmer jump. A number of useful diagnostic lines below and above the Balmer discontinuity, only slightly affected by blends, with simple doublet and triplet Zeeman pattern have been identified from the comparison between synthetic spectra computed with the SYNTHMAG code and the high resolution and S/Nspectra obtained in unpolarized light with the ESO VLT UVES spectrograph. For all three stars of our sample, HD 965, HD 116114 and 33 Lib, an increase of the magnetic field strength of the order of a few hundred Gauss has been detected bluewards of the Balmer discontinuity. These results should be taken into account in future modelling of the geometric structure of Ap star magnetic fields and the determination of the chemical abundances in Ap stars with strong magnetic fields.

Some recent observations of the abundances of s-process, r-process, and αelements in metal-poor stars have led to a new scenario for their formation. According to this scenario, these stars were born in a globular cluster and accreted the s-process enriched gas expelled by cluster stars of higher-mass, thereby modifying their surface abundances. Later on, these polluted stars evaporated from the globular cluster to constitute an important fraction of the current halo population. In addition, there are now many direct observations of abundance anomalies not only in globular cluster giant stars but also in subgiant and main-sequence stars. Accretion again provides a plausible explanation for (at least some of) these peculiarities. Here we investigate further the efficiency of the accretion scenario. We find that in concentrated clusters with large escape velocities, accretion is very efficient and can indeed lead to major modifications of the stellar surface abundances.

We report the discovery of a transiting planet with an orbital period of 1.36 days orbiting the brighter component of the visual binary star BD -07 436. The host star, WASP-77 A, is a moderately bright G8 Vstar (V= 10.3) with a metallicity close to solar ([Fe/H] = 0.0 ± 0.1). The companion star, WASP-77 B, is a K-dwarf approximately 2 mag fainter at a separation of approximately 3?. The spectrum of WASP-77 A shows emission in the cores of the CaiiH and K lines, indicative of moderate chromospheric activity. The Wide Angle Search for Planets (WASP) light curves show photometric variability with a period of 15.3 days and an amplitude of about 0.3% that is probably due to the magnetic activity of the host star. We use an analysis of the combined photometric and spectroscopic data to derive the mass and radius of the planet (1.76 ± 0.06 MJup, 1.21 ± 0.02 RJup). The age of WASP-77 A estimated from its rotation rate (?1 Gyr) agrees with the age estimated in a similar way for WASP-77 B (?0.6 Gyr) but is in poor agreement with the age inferred by comparing its effective temperature and density to stellar models (?8 Gyr). Follow-up observations of WASP-77 Ab will make a useful contribution to our understanding of the influence of binarity and host star activity on the properties of hot Jupiters.

The 16OH/18OH?and OD/OH?isotope ratios are measured in the Oort-Cloud comet C/2002?T7 (LINEAR) through ground-based observations of the OH A2?+- X2?iultraviolet bands at 3063???(0,?0) and 3121???(1,?1) obtained with the Very Large Telescope (VLT) feeding the Ultraviolet-Visual Echelle Spectrograph (UVES). From the 16OH/18OH?ratio, we find 16O/18O?=?425 ?55, equal within the uncertainties to the terrestrial value and to the ratio measured in other comets, although marginally smaller. We also estimate OD/OH?from which we derive D/H = 2.5 ?0.7?10-4in water. This value is compatible with the water D/H ratios evaluated in other comets and is marginally higher than the terrestrial value.

The $^{12}$C$^{14}$N/$^{12}$C$^{15}$N and $^{12}$C$^{14}$N/$^{13}$C$^{14}$N  isotopic ratios have been determined in comets C/1995 O1 (Hale-Bopp), C/2001 Q4 (NEAT) and C/2003 K4 (LINEAR) at heliocentric distances of, respectively, 2.7, 3.7 and 2.6 AU. These ratios have also been measured at $r\sim1$ AU. No significant differences were found between all determinations, nor with the value obtained for other comets. If confirmed, the discrepancy between the nitrogen isotopic ratios from optical and millimeter measurements on CN and HCN would rule out HCN as a major parent of the cometary CN radicals.

We announce the discovery of the transiting hot Jupiter WASP-157b in a 3.95-d orbit around a V= 12.9 G2 main-sequence star. This moderately inflated planet has a Saturn-like density, with a mass of 0.57 ± 0.10 MJupand a radius of 1.06 ± 0.05 RJup. We do not detect any rotational or phase curve modulations, nor the secondary eclipse, with conservative semi-amplitude upper limits of 250 and 20 ppm, respectively.

We present the discovery by the WASP-South survey of three planets transiting moderately bright stars (V ? 11). WASP-120 b is a massive (4.85 MJup) planet in a 3.6-day orbit that we find likely to be eccentric () around an F5 star. WASP-122 b is a hot Jupiter (1.28 MJup, 1.74 RJup) in a 1.7-day orbit about a G4 star. Our predicted transit depth variation caused by the atmosphere of WASP-122 b suggests it is well suited to characterization. WASP-123 b is a hot Jupiter (0.90 MJup, 1.32 RJup) in a 3.0-day orbit around an old (?7 Gyr) G5 star.

We report the discovery of WASP-43b, a hot Jupiter transiting a K7V star every 0.81 d. At 0.6-M⊙the host star has the lowest mass of any star currently known to host a hot Jupiter. It also shows a 15.6-d rotation period. The planet has a mass of 1.8 MJup, a radius of 0.9 RJup, and with a semi-major axis of only 0.014 AU has the smallest orbital distance of any known hot Jupiter. The discovery of such a planet around a K7V star shows that planets with apparently short remaining lifetimes owing to tidal decay of the orbit are also found around stars with deep convection zones.

We report on spectroscopic and photometric observations through transits of the exoplanets WASP-22b and WASP-26b, intended to determine the systems’ spin-orbit angles. We combine these data with existing data to refine the system parameters. We measure a sky-projected spin-orbit angle of 22 ± 16° for WASP-22b, showing the planet’s orbit to be prograde and, perhaps, slightly misaligned. We do not detect the Rossiter-McLaughlin effect of WASP-26b due to its low amplitude and observation noise. We place 3-σupper limits on orbital eccentricity of 0.063 for WASP-22b and 0.050 for WASP-26b. After refining the drift in the systemic velocity of WASP-22 found by Maxted et al. (2010, AJ, 140, 2007), we find the third body in the system to have a minimum-mass of 5.3  ±  0.3 MJup(a3/ 5 AU)2, where a3is the orbital distance of the third body.

We report the discovery by the WASP transit survey of a giant planet in a close orbit (0.0295  ±  0.0009 AU) around a moderately bright (V= 11.6, K= 10) G9 dwarf (0.89  ±  0.08   M⊙, 0.84  ±  0.03   R⊙) in the Southern constellation Eridanus. Thanks to high-precision follow-up photometry and spectroscopy obtained by the telescopes TRAPPIST and Euler, the mass and size of this planet, WASP-50 b, are well constrained to 1.47  ±  0.09   MJupand 1.15  ±  0.05   RJup, respectively. The transit ephemeris is 2   455   558.6120 (±0.0002) + N×  1.955096 (±0.000005) HJDUTC. The size of the planet is consistent with basic models of irradiated giant planets. The chromospheric activity (\hbox{$\log R'_{HK} = -4.67$}) and rotational period (Prot= 16.3  ±  0.5 days) of the host star suggest an age of 0.8  ±  0.4 Gy that is discrepant with a stellar-evolution estimate based on the measured stellar parameters (ρ∗= 1.48  ±  0.10 ρ⊙, Teff= 5400  ±  100 K, [Fe/H] = −0.12  ±  0.08) which favors an age of 7  ±  3.5 Gy. This discrepancy could be explained by the tidal and magnetic influence of the planet on the star, in good agreement with the observations that stars hosting hot Jupiters tend to show faster rotation and magnetic activity. We measure a stellar inclination of \hbox{$84_{-31}^{+6}$}deg, disfavoring a high stellar obliquity. Thanks to its large irradiation and the relatively small size of its host star, WASP-50 b is a good target for occultation spectrophotometry, making it able to constrain the relationship between hot Jupiters’ atmospheric thermal profiles and the chromospheric activity of their host stars.

We report on the discovery of a hot Jupiter-type exoplanet, CoRoT-17b, detected by the CoRoT satellite. It has a mass of 2.43  ±  0.30 MJupand a radius of 1.02  ±  0.07 RJup, while its mean density is 2.82  ±  0.38 g/cm3. CoRoT-17b is in a circular orbit with a period of 3.7681  ±  0.0003 days. The host star is an old (10.7  ±  1.0 Gyr) main-sequence star, which makes it an intriguing object for planetary evolution studies. The planet’s internal composition is not well constrained and can range from pure H/He to one that can contain  ~380 earth masses of heavier elements.

We report the discovery of a new transiting planet in the southern hemisphere. It was found by the WASP-south transit survey and confirmed photometrically and spectroscopically by the 1.2 m Swiss Euler telescope, LCOGT 2m Faulkes South Telescope, the 60 cm TRAPPIST telescope, and the ESO 3.6 m telescope. The orbital period of the planet is 2.94 days. We find that it is a gas giant with a mass of 0.88 ± 0.10   MJand an estimated radius of 0.96 ± 0.05   RJ. We obtained spectra during transit with the HARPS spectrograph and detect the Rossiter-McLaughlin effect despite its small amplitude. Because of the low signal-to-noise ratio of the effect and a small impact parameter, we cannot place a strong constraint on the projected spin-orbit angle. We find two conflicting values for the stellar rotation. We find, via spectral line broadening, that vsin   I= 2.2 ± 0.3 km s-1, while applying another method, based on the activity level using the index \hbox{$\log\,R'_{\rm HK}$}, gives an equatorial rotation velocity of only v= 1.35 ± 0.20 km s-1. Using these as priors in our analysis, the planet might be either misaligned or aligned. This result raises doubts about the use of such priors. There is evidence of neither eccentricity nor any radial velocity drift with time.

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.

High-resolution far-infrared and sub-millimetre spectroscopy of water lines is an important tool to understand the physical and chemical properties of cometary atmospheres. We present observations of several rotational ortho- and para-water transitions in comet C/2008 Q3 (Garradd) performed with HIFI on Herschel. These observations have provided the first detection of the 212–101(1669 GHz) ortho and 111–000(1113 GHz) para transitions of water in a cometary spectrum. In addition, the ground-state transition 110–101at 557 GHz is detected and mapped. By detecting several water lines quasi-simultaneously and mapping their emission we can constrain the excitation parameters in the coma. Synthetic line profiles are computed using excitation models which include excitation by collisions, solar infrared radiation, and radiation trapping. We obtain the gas kinetic temperature, constrain the electron density profile, and estimate the coma expansion velocity by analyzing the map and line shapes. We derive water production rates of 1.7–2.8 × 1028s-1over the range rh= 1.83–1.85 AU.

Comet C/2006 W3 (Christensen) was observed in November 2009 at 3.3 AU from the Sun with Herschel.The PACS instrument acquired images of the dust coma in 70-μm and 160-μm filters and spectra covering several H2O rotational lines. Spectra in the range 450–1550 GHz were acquired with SPIRE. The comet emission continuum from 70 to 672 μm was measured, but no lines were detected. The spectral energy distribution indicates thermal emission from large particles and provides a measure of the size distribution index and dust production rate. The upper limit to the water production rate is compared to the production rates of other species (CO, CH3OH, HCN, H2S, OH) measured with the IRAM 30-m and Nançay telescopes. The coma is found to be strongly enriched in species more volatile than water, in comparison to comets observed closer to the Sun. The CO to H2O production rate ratio exceeds 220%. The dust-to-gas production rate ratio is on the order of 1.

We have obtained the first continuous disk averaged spectrum of Mars from 450 to 1550 Ghz using the Herschel-SPIRE Fourier-transform spectrometer. The spectrum was obtained at a constant resolution of 1.4 GHz across the whole band. The flux from the planet is such that the instrument was operated in “bright source” mode to prevent saturation of the detectors. This was the first successful use of this mode and in this work we describe the method used for observing Mars together with a detailed discussion of the data reduction techniques required to calibrate the spectrum. We discuss the calibration accuracy obtained and describe the first comparison with surface and atmospheric models. In addition to a direct photometric measurement of the planet the spectrum contains the characteristic transitions of 12CO from J 5–4 to J 13–12 as well as numerous H2O transitions. Together these allow the comparison to global atmospheric models allowing the mean mixing ratios of water and 12CO to be investigated. We find that it is possible to match the observed depth of the absorption features in the spectrum with a fixed water mixing ratio of 1×10-4and a 12CO mixing ratio of 9×10-4.

We report on the initial analysis of a Herschel-PACS full range spectrum of Neptune, covering the 51–220 μm range with a mean resolving power of ~3000, and complemented by a dedicated observation of CH4at 120 μm. Numerous spectral features due to HD (R(0) and R(1)), H2O, CH4, and CO are present, but so far no new species have been found. Our results indicate that (i) Neptune's mean thermal profile is warmer by ~3 K than inferred from the Voyagerradio-occultation; (ii) the D/H mixing ratio is (4.5 ±1) × 10-5, confirming the enrichment of Neptune in deuterium over the protosolar value (~2.1 × 10-5); (iii) the CH4mixing ratio in the mid stratosphere is (1.5 ±0.2) × 10-3, and CH4appears to decrease in the lower stratosphere at a rate consistent with local saturation, in agreement with the scenario of CH4stratospheric injection from Neptune's warm south polar region; (iv) the H2O stratospheric column is (2.1 ±0.5) × 1014cm-2but its vertical distribution is still to be determined, so the H2O external flux remains uncertain by over an order of magnitude; and (v) the CO stratospheric abundance is about twice the tropospheric value, confirming the dual origin of CO suspected from ground-based millimeter/submillimeter observations.

We report on the initial analysis of a Herschel-PACS full range spectrum of Neptune, covering the 51–220 μm range with a mean resolving power of ~3000, and complemented by a dedicated observation of CH4at 120 μm. Numerous spectral features due to HD (R(0) and R(1)), H2O, CH4, and CO are present, but so far no new species have been found. Our results indicate that (i) Neptune's mean thermal profile is warmer by ~3 K than inferred from the Voyagerradio-occultation; (ii) the D/H mixing ratio is (4.5 ±1) × 10-5, confirming the enrichment of Neptune in deuterium over the protosolar value (~2.1 × 10-5); (iii) the CH4mixing ratio in the mid stratosphere is (1.5 ±0.2) × 10-3, and CH4appears to decrease in the lower stratosphere at a rate consistent with local saturation, in agreement with the scenario of CH4stratospheric injection from Neptune's warm south polar region; (iv) the H2O stratospheric column is (2.1 ±0.5) × 1014cm-2but its vertical distribution is still to be determined, so the H2O external flux remains uncertain by over an order of magnitude; and (v) the CO stratospheric abundance is about twice the tropospheric value, confirming the dual origin of CO suspected from ground-based millimeter/submillimeter observations.

Comet C/2006 W3 (Christensen) was observed in November 2009 at 3.3 AU from the Sun with Herschel.The PACS instrument acquired images of the dust coma in 70-μm and 160-μm filters and spectra covering several H2O rotational lines. Spectra in the range 450–1550 GHz were acquired with SPIRE. The comet emission continuum from 70 to 672 μm was measured, but no lines were detected. The spectral energy distribution indicates thermal emission from large particles and provides a measure of the size distribution index and dust production rate. The upper limit to the water production rate is compared to the production rates of other species (CO, CH3OH, HCN, H2S, OH) measured with the IRAM 30-m and Nançay telescopes. The coma is found to be strongly enriched in species more volatile than water, in comparison to comets observed closer to the Sun. The CO to H2O production rate ratio exceeds 220%. The dust-to-gas production rate ratio is on the order of 1.

We have obtained the first continuous disk averaged spectrum of Mars from 450 to 1550 Ghz using the Herschel-SPIRE Fourier-transform spectrometer. The spectrum was obtained at a constant resolution of 1.4 GHz across the whole band. The flux from the planet is such that the instrument was operated in “bright source” mode to prevent saturation of the detectors. This was the first successful use of this mode and in this work we describe the method used for observing Mars together with a detailed discussion of the data reduction techniques required to calibrate the spectrum. We discuss the calibration accuracy obtained and describe the first comparison with surface and atmospheric models. In addition to a direct photometric measurement of the planet the spectrum contains the characteristic transitions of 12CO from J 5–4 to J 13–12 as well as numerous H2O transitions. Together these allow the comparison to global atmospheric models allowing the mean mixing ratios of water and 12CO to be investigated. We find that it is possible to match the observed depth of the absorption features in the spectrum with a fixed water mixing ratio of 1×10-4and a 12CO mixing ratio of 9×10-4.

High-resolution far-infrared and sub-millimetre spectroscopy of water lines is an important tool to understand the physical and chemical properties of cometary atmospheres. We present observations of several rotational ortho- and para-water transitions in comet C/2008 Q3 (Garradd) performed with HIFI on Herschel. These observations have provided the first detection of the 212–101(1669 GHz) ortho and 111–000(1113 GHz) para transitions of water in a cometary spectrum. In addition, the ground-state transition 110–101at 557 GHz is detected and mapped. By detecting several water lines quasi-simultaneously and mapping their emission we can constrain the excitation parameters in the coma. Synthetic line profiles are computed using excitation models which include excitation by collisions, solar infrared radiation, and radiation trapping. We obtain the gas kinetic temperature, constrain the electron density profile, and estimate the coma expansion velocity by analyzing the map and line shapes. We derive water production rates of 1.7–2.8 × 1028s-1over the range rh= 1.83–1.85 AU.

We report on the composition of the Halley-family comet (HFC) 8P/Tuttle investigated with high-dispersion near-infrared spectroscopic observations. The observations were carried out at the ESO VLT (Very Large Telescope) with the CRIRES instrument as part of a multi-wavelength observation campaign of 8P/Tuttle performed in late January and early February 2008. Radar observations suggested that 8P/Tuttle is a contact binary, and it was proposed that these components might be heterogeneous in chemistry. We determined mixing ratios of organic volatiles with respect to H2O and found that mixing ratios were consistent with previous near infrared spectroscopic observations obtained in late December 2007 and in late January 2008. It has been suggested that because 8P/Tuttle is a contact binary, it might be chemically heterogeneous. However, we find no evidence for chemical heterogeneity within the nucleus of 8P/Tuttle. We also compared the mixing ratios of organic molecules in 8P/Tuttle with those of both other HFCs and long period comets (LPCs) and found that HCN, C2H2, and C2H6are depleted whereas CH4and CH3OH have normal abundances. This may indicate that 8P/Tuttle was formed in a different region of the early solar nebula than other HFCs and LPCs. We estimated the conversion efficiency from C2H2to C2H6by hydrogen addition reactions on cold grains by employing the C2H6/(C2H6+C2H$_{2})$ratio. The C2H6/(C2H6+C2H$_{2})$ratio in 8P/Tuttle is consistent with the ratios found in other HFCs and LPCs within the error bars. We also discuss the source of C2and CN based on our observations and conclude that the abundances of C2H2and C2H6are insufficient to explain the C2abundances in comet 8P/Tuttle and that the abundance of HCN is insufficient to explain the CN abundances in the comet, so at least one additional parent is needed for each species, as pointed out in previous study.

We report on the composition of the Halley-family comet (HFC) 8P/Tuttle investigated with high-dispersion near-infrared spectroscopic observations. The observations were carried out at the ESO VLT (Very Large Telescope) with the CRIRES instrument as part of a multi-wavelength observation campaign of 8P/Tuttle performed in late January and early February 2008. Radar observations suggested that 8P/Tuttle is a contact binary, and it was proposed that these components might be heterogeneous in chemistry. We determined mixing ratios of organic volatiles with respect to H2O and found that mixing ratios were consistent with previous near infrared spectroscopic observations obtained in late December 2007 and in late January 2008. It has been suggested that because 8P/Tuttle is a contact binary, it might be chemically heterogeneous. However, we find no evidence for chemical heterogeneity within the nucleus of 8P/Tuttle. We also compared the mixing ratios of organic molecules in 8P/Tuttle with those of both other HFCs and long period comets (LPCs) and found that HCN, C2H2, and C2H6are depleted whereas CH4and CH3OH have normal abundances. This may indicate that 8P/Tuttle was formed in a different region of the early solar nebula than other HFCs and LPCs. We estimated the conversion efficiency from C2H2to C2H6by hydrogen addition reactions on cold grains by employing the C2H6/(C2H6+C2H$_{2})$ratio. The C2H6/(C2H6+C2H$_{2})$ratio in 8P/Tuttle is consistent with the ratios found in other HFCs and LPCs within the error bars. We also discuss the source of C2and CN based on our observations and conclude that the abundances of C2H2and C2H6are insufficient to explain the C2abundances in comet 8P/Tuttle and that the abundance of HCN is insufficient to explain the CN abundances in the comet, so at least one additional parent is needed for each species, as pointed out in previous study.

We report on the composition of the Halley-family comet (HFC) 8P/Tuttle investigated with high-dispersion near-infrared spectroscopic observations. The observations were carried out at the ESO VLT (Very Large Telescope) with the CRIRES instrument as part of a multi-wavelength observation campaign of 8P/Tuttle performed in late January and early February 2008. Radar observations suggested that 8P/Tuttle is a contact binary, and it was proposed that these components might be heterogeneous in chemistry. We determined mixing ratios of organic volatiles with respect to H2O and found that mixing ratios were consistent with previous near infrared spectroscopic observations obtained in late December 2007 and in late January 2008. It has been suggested that because 8P/Tuttle is a contact binary, it might be chemically heterogeneous. However, we find no evidence for chemical heterogeneity within the nucleus of 8P/Tuttle. We also compared the mixing ratios of organic molecules in 8P/Tuttle with those of both other HFCs and long period comets (LPCs) and found that HCN, C2H2, and C2H6are depleted whereas CH4and CH3OH have normal abundances. This may indicate that 8P/Tuttle was formed in a different region of the early solar nebula than other HFCs and LPCs. We estimated the conversion efficiency from C2H2to C2H6by hydrogen addition reactions on cold grains by employing the C2H6/(C2H6+C2H$_{2})$ratio. The C2H6/(C2H6+C2H$_{2})$ratio in 8P/Tuttle is consistent with the ratios found in other HFCs and LPCs within the error bars. We also discuss the source of C2and CN based on our observations and conclude that the abundances of C2H2and C2H6are insufficient to explain the C2abundances in comet 8P/Tuttle and that the abundance of HCN is insufficient to explain the CN abundances in the comet, so at least one additional parent is needed for each species, as pointed out in previous study.