Ammonia and other parent molecules in comet 10P/Tempel 2 from Herschel/HIFI and ground-based radio observations

The Jupiter-family comet 10P/Tempel 2 was observed during its 2010 return with the Herschel Space Observatory. We present here the observation of the (J, K) = (1, 0)-(0, 0) transition of ammonia at 572 GHz in this comet with the Heterodyne Instrument for the Far Infrared (HIFI) of Herschel. We also report on radio observations of other molecules (HCN, CH3OH, H2S and CS) obtained during the 1999 return of the comet with the CSO telescope and the JCMT, and during its 2010 return with the IRAM 30-m telescope. Molecular abundances relative to water are 0.09%, 1.8%, 0.4%, and 0.08% for HCN, CH3OH, H2S, and CS, respectively. An abundance of 0.5% for NH3 is obtained, which is similar to the values measured in other comets. The hyperfine structure of the ammonia line is resolved for the first time in an astronomical source. Strong anisotropy in the outgassing is present in all observations from 1999 to 2010 and is modelled to derive the production rates.Comment: 6 pages and 8 figures. Accepted for publication in Astronomy & Astrophysic

Vertical Water Vapor Distribution In The Atmospheres Of Uranus And Neptune As Obtained From Herschel Observations

As part of the guaranteed time key programme "Water and related chemistry in the Solar System" (KP-GT HssO) about twenty different rotational water vapor transitions have been observed in the atmospheres of Uranus and Neptune with the PACS instrument of the European Space Agency's Herschel Space Observatory. In addition the 110-101 ground-state transition of H2O at 557 GHz has been observed in both planets at the very high resolution of 1 MHz using the Herschel/HIFI instrument. Using a line-by-line radiation transfer model in combination with the Optimal Estimation Method as retrieval technique we analyze the data in terms of information content to derive the vertical distribution of water vapor. The resulting distribution, which is obtained from a simultaneous fit of the whole set of transitions, will be presented for both planets

Far Infrared Spectra of Jupiter Observed with PACS Onboard Herschel

Jupiter was observed on October 31, 2009 with the Photodetector Array Camera and Spectrometer (PACS) onboard the Herschel Space Observatory, as part of the guaranteed time key program "Water and related chemistry in the Solar System (HssO)". PACS is as an integral field spectrometer which covers the wavelength range between 55 and 210 µm with a resolving power varying from 940 to 5500. The apparent disk diameter of Jupiter was 41", and it was spatially resolved with 5 * 5 spatial pixels where each spaxel have a projected size of 9.7" * 9.7" on the sky. The observed spectra show numerous spectral features due to NH3, PH3, HD, CH4, and stratospheric H2O. We will present the initial data analysis which provides new insight into the abundances of these observed species. In addition, upper limits on the abundances of hydrogen halides (HF, HCl, HBr, and HI) will be also discussed. * T. de Graauw is also affiliated with SRON Netherlands Institute for Space Research, the Netherlands, and Leiden Observatory, University of Leiden, the Netherlands

Detection of Enceladus Torus from Submillimeter Observations with Herschel/HIFI

The presence of water vapor in the stratospheres of the Giant Planets and Titan has been established from their emission in rotational lines longwards of 30 microns. Emission in the fundamental H2O line at 557 GHz has been spectrally resolved from heterodyne observations with SWAS at Jupiter and Saturn and ODIN at Jupiter, showing emission line-widths of about 20 km/s, due to planetary rotation. Initial observations of Saturn with the HIFI instrument on Herschel, performed in June 2009, revealed an additional 20 % deep, 5 km/s broad absorption superimposed to the emission, that was not seen in the SWAS observation performed in 1999 (Bergin et al. 2000). This absorption is certainly not due to water in Saturn itself, as the brightness temperature in the line core would indicate implausibly cold temperatures ( 95 K) in Saturn's upper atmosphere, and as the line-width is too narrow. Instead, we interpret it as water vapor absorption along the line-of-sight coming from the Enceladus H2O torus, the difference with the SWAS results being presumably related to the different viewing geometries. We developed an excitation model for water in Enceladus torus including excitation by solar and Saturn's radiation. Extended observations performed in June 2010, and covering the H2O 557, 987, 1113 and 1670 GHz (including a 5-point map at this frequency) confirm this interpretation, as does the fact that the 1097 GHz H2O line does not show absorption. An initial modelling of the data indicates line-of-sight water column densities of (1-3)x1013 cm-2. These observations provide a new method to study physical conditions in the Enceladus torus

Mapping water in Jupiter with Herschel/HIFI

A major discovery of ISO was the detection of water in the upper atmospheres of the four giant planets and Titan (Feuchtgruber et al, 1997; Coustenis et al, 1998), implying the existence of external sources of water. This oxygen supply, which manifests itself also through the presence of CO2 and CO in these atmospheres, may have several sources: (i) a permanent flux from interplanetary dust particles produced from asteroid collisions and from comet activity (Prather et al,1978), (ii) local sources from planetary environments (rings, satellites) (Strobel and Yung, 1979; Prangé et al, 2006), (iii) cometary ``Shoemaker-Levy 9 (SL9) type'' impacts (Lellouch et al, 1995). Disentangling the various sources at Jupiter is a key objective of the Herschel Space Observatory key program HssO (Hartogh et al, 2009). Herschel/HIFI observed H2O in Jupiter at 1669 GHz in a 5x5 point map on July 7, 2010. From this observation, we will present and discuss the search for latitudinal variability of H2O in Jupiter. Acknowledgement: Research by T. Cavalié was supported by the Fondation des Amis des Sciences. References: Coustenis et al, A&A 336,L85-L89. Feuchtgruber et al, 1997. Nature 389, 159-162. Hartogh et al, 2009. Planet. Space Sci. 57, 1596-1606. Lellouch et al, 1995. Nature 373, 592-595. Prangé et al, 2006. Icarus 180, 379-392. Prather, 1978. ApJ 223, 1072-1081. Strobel & Yung, 1979. Icarus 37, 256-263

Water, hydrogen cyanide, and dust production from the distant comet 29P/Scwassmann-Wachmann 1

Comet 29P/Schwassmann-Wachmann is a periodic comet, also classified as a Centaur, orbiting on a nearly circular orbit at 6 au from the Sun. It is well known for its permanent activity driven by CO outgassing, and its episodic outbursts. Comet 29P was observed in 2010--2011 with the Herschel space observatory. Observations of water and ammonia were performed with the Heterodyne Instrument for the Far-Infrared (HIFI). One set of measurements was obtained two days after a major outburst (16 Apr. 2010). Images of the dust coma at 70 and 160 μ m were obtained using the Photodetector Array Camera and Spectrometer (PACS). To support these observations, observations of CO and HCN were undertaken at the 30-m telescope of the Institut de radioastronomie millimétrique (IRAM). We present an overview of this set of observations. H_2O and CO are detected. We also obtain the first detection of HCN in this distant comet. Relative abundances are similar to those measured in the coma of comet C/1995 O1 (Hale-Bopp) when at r_h = 6 au from the Sun, but strongly differ from coma compositions at r_h = 1 au. The line profiles show evidence that both H_2O, HCN are released from long-lived icy grains. Detailed modeling of water production from icy-grain suggests continuous release of icy grains from the nucleus. The thermal emission from the nucleus is detected in the PACS 70 μ m images. The thermal emission from dust grains is analyzed with a thermal model of dust emission, which takes into account the dust size distribution. Both the size index and the dust production rate are measured

The Physical Structure and Chemical Composition of Neptune's Atmosphere from Combined Herschel and Spitzer Spectral Observations

International audienceWe report the analysis of thermal-infrared observations of Neptune's disk by experiments on the Spitzer and Herschel Space Telescopes. The Spitzer data were obtained by the IRS instrument at wavelengths between 5.2 and 21.5 microns at a spectral resolving power, R 70, and at wavelengths between 10 and 21.5 microns at R 600. The Herschel observations were made by the PACS instrument's integral field spectrometer between 51 and 220 microns at R 3000, within the framework of the Key Project, ``Water and Related Chemistry in the Solar System''. Our analysis is set in the context of lower-resolution spectra obtained by the ISO LWS and SWS spectrometers covering wavelengths between 28 and 185 microns and the Akari IRC spectrometer covering wavelengths between 5.8 and 13.3 microns at R 40, together with spatially resolved ground-based studies of thermal emission. Our results indicate that that global-mean tropospheric temperatures are lower than those derived from the Voyager radio-occultation experiment, and consistent with the ISO results. Preliminary results (Lellouch et al. 2010 Astron. & Astrophys. In press) indicate that the D/H ratio is 4.5±1.0 x 10-5, consistent with enrichment of deuterium over the protosolar value, and the stratospheric column of H2O is 2.1±0.5 x 1014 cm-2. The peak CH4 abundance in the stratosphere is orders of magnitude larger than if it were cold-trapped below the mean 54-Kelvin tropopause minimum temperature - but consistent with injection from Neptune's warmer south polar region. Good fits to a variety of other stratospheric emission features are obtained: CO, CH3, CO2, C2H2, C2H4, C2H6, C3H8, C4H2. It is also possible to obtain a better fit to a spectral region dominated by C2H6 emission by adding 50-100 ppt of C6H6

Comet 29P/Schwassmann-Wachmann Observed with the Herschel Space Observatory: Detection of Water Vapour and Dust Far-IR Thermal Emission

The distant comet 29P/Schwassmann-Wachmann was observed with the HIFI, PACS and SPIRE instruments aboard the Herschel Space Observatory, as part of the guaranteed time key programme "Water and related chemistry in the Solar System" (KP-GT HssO). Supporting observations of the 230 GHz CO line were carried out with the IRAM 30-m telescope. The HIFI observations of the 557 GHz H2O line were performed on 19.05 April 2010, about 2 days after a major outburst, and on 11.02 May 2010, when 29P was in a more quiescent phase. H2O was detected on both dates with a production rate corresponding to about 1/10th the CO production, assuming near-nucleus production. The H2O line shape is consistent with release of water vapour from icy grains. PACS and SPIRE imaging data from 70 to 500 micrometers were acquired mid-June 2010 when the comet was in a quiescent phase. The continuum emission detected in the 70-μm and 160-μm PACS images is weakly extended with respect to the PSF, suggesting a major contribution from the nucleus or from slowly moving large grains