D/H Ratios on Saturn and Jupiter from Cassini CIRS

Journal Article · Wed Nov 01 04:00:00 EDT 2017 · The Astronomical Journal (Online)

DOI:https://doi.org/10.3847/1538-3881/AA899D· OSTI ID:22863017

Pierel, J. D. R.; Nixon, C. A.; Bjoraker, G. L.; Achterberg, R. K.; Hesman, B. E.; Flasar, F. M. ^[1]; Lellouch, E.; Bézard, B. ^[2]; Fletcher, L. N. ^[3]; Irwin, P. G. J. ^[4]

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1. Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
2. LESIA-Observatoire de Paris, CNRS, UPMC, Université Paris–Diderot, 5 place Jules Janssen, F-92195 Meudon (France)
3. Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom)
4. Department of Physics, Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford OX1 3PU (United Kingdom)

We present new measurements of the deuterium abundance on Jupiter and Saturn, showing evidence that Saturn’s atmosphere contains less deuterium than Jupiter’s. We analyzed far-infrared spectra from the Cassini Composite Infrared Spectrometer to measure the abundance of HD on both giant planets. Our estimate of the Jovian D/H = (2.95 ± 0.55) × 10{sup −5} is in agreement with previous measurements by ISO/SWS: (2.25 ± 0.35) × 10{sup −5}, and the Galileo probe: (2.6 ± 0.7) × 10{sup −5}. In contrast, our estimate of the Saturn value of (2.10 ± 0.13) × 10{sup −5} is somewhat lower than on Jupiter (by a factor of 0.71{sub −0.15}{sup +0.22}), contrary to model predictions of a higher ratio: Saturn/Jupiter = 1.05–1.20. The Saturn D/H value is consistent with estimates for hydrogen in the protosolar nebula (2.1 ± 0.5) × 10{sup −5}, but its apparent divergence from the Jovian value suggests that our understanding of planetary formation and evolution is incomplete, which is in agreement with previous work.

• OSTI ID: 22863017
• Journal Information: The Astronomical Journal (Online), Journal Name: The Astronomical Journal (Online) Journal Issue: 5 Vol. 154; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DEUTERIUM
FORECASTING
HYDROGEN
INFRARED SPECTRA
INFRARED SPECTROMETERS
JUPITER PLANET
PLANETARY ATMOSPHERES
SATELLITES
SATURN PLANET