Küppers, M.[European Space Astronomy Center, Madrid, Spain]
Lara, L. M.[Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain]
Lis, D. C.[California Institute of Technology, Pasadena, USA]
Medvedev, A. S.[Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany]
Rengel, M.[Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany]
Sagawa, H.[Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany]
Swinyard, B.[Rutherford Appleton Laboratory, Oxfordshire, U K]
Szutowicz, S.[Space Research Centre, Polish Academy of Science, Warszawa, Poland]
Bensch, F.[Deutsches Zentrum für Luft- und Raumfahrt (DLR), Bonn, Germany]
Bergin, E.[University of Michigan, Ann Arbor, USA]
Billebaud, F.[Université de Bordeaux, Observatoire Aquitain des Sciences de l'Univers, CNRS, UMR 5804, Laboratoire d'Astrophysique de Bordeaux, France]
Biver, N.[LESIA, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon, France]
Blake, G. A.[JPL, California Institute of Technology, Pasadena, USA]
Blommaert, J A D L[Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Belgium]
Cernicharo, J.[Laboratorio de Astrofísica Molecular, CAB. INTA-CSIC, Spain]
Courtin, R.[LESIA, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon, France]
[en] planets and satellites: atmospheres ; planets and satellites: individual: Neptune ; planets and satellites: composition ; techniques: spectroscopic
[en] 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 CH[SUB]4[/SUB] at 120 μm. Numerous spectral features due to HD (R(0) and R(1)), H[SUB]2[/SUB]O, CH[SUB]4[/SUB], 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 Voyager radio-occultation; (ii) the D/H mixing ratio is (4.5 ± 1) × 10[SUP]-5[/SUP], confirming the enrichment of Neptune in deuterium over the protosolar value (~2.1 × 10[SUP]-5[/SUP]); (iii) the CH[SUB]4[/SUB] mixing ratio in the mid stratosphere is (1.5 ± 0.2) × 10[SUP]-3[/SUP], and CH[SUB]4[/SUB] appears to decrease in the lower stratosphere at a rate consistent with local saturation, in agreement with the scenario of CH[SUB]4[/SUB] stratospheric injection from Neptune's warm south polar region; (iv) the H[SUB]2[/SUB]O stratospheric column is (2.1 ± 0.5) × 10[SUP]14[/SUP] cm[SUP]-2[/SUP] but its vertical distribution is still to be determined, so the H[SUB]2[/SUB]O 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. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
[LESIA, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon, France]
