Deuterium-enriched water ties planet-forming disks to comets and protostars.

Water is a fundamental molecule in the star and planet formation process, essential for catalysing the growth of solid material and the formation of planetesimals within disks1,2. However, the water snowline and the HDO:H₂O ratio within proto-planetary disks have not been well characterized because water only sublimates at roughly 160 K (ref. 3), meaning that most water is frozen out onto dust grains and that the water snowline radii are less than 10 AU (astronomical units)4,5. The sun-like protostar V883 Ori (M_* = 1.3 M_⊙)6 is undergoing an accretion burst7, increasing its luminosity to roughly 200 L_⊙ (ref. 8), and previous observations suggested that its water snowline is 40–120 AU in radius6,9,10. Here we report the direct detection of gas phase water (HDO and H 2 18 O ) from the disk of V883 Ori. We measure a midplane water snowline radius of approximately 80 AU, comparable to the scale of the Kuiper Belt, and detect water out to a radius of roughly 160 AU. We then measure the HDO:H₂O ratio of the disk to be (2.26 ± 0.63) × 10⁻³. This ratio is comparable to those of protostellar envelopes and comets, and exceeds that of Earth’s oceans by 3.1σ. We conclude that disks directly inherit water from the star-forming cloud and this water becomes incorporated into large icy bodies, such as comets, without substantial chemical alteration.Direct detection of gas phase water from the disk of V883 Ori indicates that disks directly inherit water from the star-forming cloud that becomes incorporated into large icy bodies without notable chemical alteration. [ABSTRACT FROM AUTHOR]