Pristine Ices In A Planet-forming Disk Revealed By Heavy Water

Water is essential to our understanding of the planet-formation process and habitability on Earth.

Although trace amounts of water are seen across all phases of star and planet formation, the bulk of the water reservoir often goes undetected, hiding crucial parts of its journey from giant molecular clouds to planets. This raises the question of whether water molecules in comets and (exo-)planets is largely inherited from the interstellar medium or if the water molecules are destroyed and then reformed in the disk.

Water isotopologue ratios involving doubly deuterated water (D₂O) are a sensitive tracer to answer this question. We present strong evidence of inheritance through an enhancement of D₂O in the outbursting V883 Ori disk. The high D₂O/H₂O ratio of (3.2±1.2)×10−5 is consistent with values seen in protostellar envelopes and a comet and is two orders of magnitude higher than expected if water is reprocessed.

The high deuteration of the heaviest isotopologues D₂O/HDO = (2.3±1.0)×HDO/H₂O further establishes the inheritance of water. We conclude that water ice in disks originates from the earliest phases of star formation, providing the missing link between cold dark clouds and (exo-)comets.

Margot Leemker, John J. Tobin, Stefano Facchini, Pietro Curone, Alice S. Booth, Kenji Furuya, Merel L. R. van ‘t Hoff

Comments: Published in Nature Astronomy (this https URL). Version after refereeing but before proofing
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2510.19919 [astro-ph.EP] (or arXiv:2510.19919v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2510.19919
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Related DOI:
https://doi.org/10.1038/s41550-025-02663-y
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Submission history
[v1] Wed, 22 Oct 2025 18:00:03 UTC (3,960 KB)
https://arxiv.org/abs/2510.19919
Astrobiology, Astrochemistry, Astronomy,