Deuterated Water Ice On The Satellites Of Saturn

The deuterium to hydrogen ratio in water ice in a planetary body carries important information on the history of water processing and delivery in the protostellar nebula.

For a giant planet satellite, the D/H ratio is also affected by the processes and temperatures of the circumplanetary or circumstellar environment in which the satellites formed.

Here we present robust JWST spectroscopic detections of the 4.14 μm O-D stretch absorption line (analogous to the 3 μm water O-H stretch) on the mid-sized Saturnian satellites and use these detections to infer a D/H ratio on each satellite.

Within the limitations of the technique, we find that all of the satellites are consistent with having a D/H ratio of about 1.5× Vienna Standard Mean Ocean Water (VSMOW), which is about an order of magnitude higher than the value of the atmosphere of Saturn.

A much higher previously reported D/H ratio for Phoebe is ruled out at the 10σ level, and a 3σ upper limit of 2.3 × VSMOW is obtained. The elevated D/H ratios demonstrate that the solid planetesimals and pebbles that built the satellites never sublimed and re-equilibrated with the gaseous circumplanetary disk.

The similarity of the D/H measurements across all satellites suggest that the D/H ratio of water ice in the vicinity of Saturn at the time of satellite formation was also approximately 1.5 × VSMOW.

Michael E. Brown, Samantha K. Trumbo, M. Ryleigh Davis, Swaroop Chandra

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2510.14859 [astro-ph.EP] (or arXiv:2510.14859v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2510.14859
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Journal reference: Michael E. Brown et al 2025 Planet. Sci. J. 6 229
Related DOI:
https://doi.org/10.3847/PSJ/adfbf5
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Submission history
From: Michael Brown
[v1] Thu, 16 Oct 2025 16:33:34 UTC (122 KB)
https://arxiv.org/abs/2510.14859

Astrobiology, Astrochemistry, Astrogeology,