D/H Ratios on Saturn and Jupiter from Cassini CIRS

Journal article

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) × 10⁻⁵ is in agreement with previous measurements by ISO/SWS: (2.25 ± 0.35) × 10⁻⁵, and the Galileo probe: (2.6 ± 0.7) × 10⁻⁵. In contrast, our estimate of the Saturn value of (2.10 ± 0.13) × 10⁻⁵ is somewhat lower than on Jupiter (by a factor of ), 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) ×10⁻⁵, 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.

Authors: Pierel, J; Nixon, C; Lellouch, E; Fletcher, L; Bjoraker, G

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: IOP Publishing
• Journal: Astronomical Journal
• Volume: 154
• Issue: 5
• Pages: 178
• Publication date: 2017-10-05
• Acceptance date: 2017-08-29
• DOI: 10.3847/1538-3881/aa899d
• EISSN: 1538-3881
• ISSN: 0004-6256
• Keywords: infrared: planetary systems; planets and satellites: gaseous planets; planets and satellites: atmospheres; planets and satellites: composition planets and satellites: formation