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Astron. Astrophys. 341, L17-L21 (1999)

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Detection of HD in the atmospheres of Uranus and Neptune: a new determination of the D/H ratio *

H. Feuchtgruber 1, E. Lellouch 2, B. Bézard 2, Th. Encrenaz 2, Th. de Graauw 3 and G.R. Davis 4

1 Max-Planck-Institut für Extraterrestrische Physik, Postfach 1603, D-85740 Garching, Germany
2 Observatoire de Paris-Meudon, 5 Place Janssen, F-92195 Meudon Cedex, France
3 Space Research Organisation of the Netherlands and Kapteyn Institute P.O. Box 800, 9700 AV Groningen, The Netherlands
4 Institute of Space and Atmospheric Studies, University of Saskatchewan, 116 Science Place, Saskatoon, S7N 5E2, Canada

Received 30 October 1998 / Accepted 13 November 1998


Observations with the Short Wavelength Spectrometer (SWS) onboard the Infrared Space Observatory (ISO) have led to the first unambiguous detection of [FORMULA] in the atmospheres of Uranus and Neptune, from its R(2) rotational line at [FORMULA]m. Using S(0) and S(1) quadrupolar lines of [FORMULA] at 28.2 and 17.0 µm as atmospheric thermometers, we derive [FORMULA] ratios of [FORMULA] and [FORMULA] on Uranus and Neptune respectively. This confirms that compared to Jupiter and Saturn, Uranus and Neptune have been enriched in deuterium by the mixing of their atmospheres with D-rich protoplanetary ices. Assuming complete mixing of the planets, the [FORMULA] ratio in these ices is however found to be lower than in cometary ices.

Key words: planets and satellites: general – planets and satellites: individual: Neptune – planets and satellites: individual: Uranus – solar system: formation – infrared: solar system

* Based on observations made with ISO, a project of ESA with participation of ISAS and NASA, and the SWS, a joint project of SRON and MPE (DARA grants no 50 QI9402 3 and 50 QI 8610 8) with contributions from KU Leuven, Steward Observatory and Phillips Laboratory.

Send offprint requests to: H. Feuchtgruber (fgb@mpe.mpg.de)

© European Southern Observatory (ESO) 1999

Online publication: November 26, 1998