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Published September 10, 2025 | Version Published
Journal Article Open

Cosmic Cascades: How Disk Substructure Regulates the Flow of Water to Inner Planetary Systems

Creators

  • 1. ROR icon University of Exeter
  • 2. ROR icon Texas State University
  • 3. ROR icon University of Wisconsin–Madison
  • 4. ROR icon University College London
  • 5. ROR icon University of Michigan–Ann Arbor
  • 6. ROR icon Vassar College
  • 7. ROR icon Jet Propulsion Lab
  • 8. ROR icon California Institute of Technology
  • 9. ROR icon University of Arizona
  • 10. ROR icon Columbia University
  • 11. Center for Star and Planet Formation, Globe Institute, Øster Voldgade 5, 1350 Copenhagen, Denmark
  • 12. ROR icon European Southern Observatory
  • 13. ROR icon University of Virginia
  • 14. ROR icon Harvard-Smithsonian Center for Astrophysics

Abstract

The influx of icy pebbles to the inner regions of protoplanetary disks constitutes a fundamental ingredient in most planet formation theories. The observational determination of the magnitude of this pebble flux and its dependence on disk substructure (disk gaps as pebble traps) would be a significant step forward. In this work, we analyze a sample of 21 T Tauri disks (with ages ≈0.5–2 Myr) using JWST/MIRI spectra homogeneously reduced with the JDISCS pipeline and high-angular-resolution Atacama Large Millimeter/submillimeter Array (ALMA) continuum data. We find that the 1500/6000 K water line flux ratio measured with JWST—a tracer of cold water vapor and pebble drift near the snow line—correlates with the radial location of the innermost dust gap in ALMA continuum observations (ranging from 8.7 to 69 au), confirming predictions from recent models that study connections between the inner and outer disk reservoirs. We develop a population synthesis exploration of pebble drift in gapped disks and find a good match to the observed trend for early and relatively effective gaps, while scenarios where pebble drift happens quickly, gaps are very leaky, or where gaps form late, are all disfavored on a population level. Inferred snow line pebble mass fluxes (ranging between 10−6 and 10−3 M⊕ yr−1 depending on gap position) are comparable to fluxes used in pebble accretion studies and those proposed for the inner solar system, while system-to-system variations suggest differences in the emerging planetary system architectures and water budgets.

Copyright and License

© 2025. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

We thank the reviewer for providing insightful comments that helped improve the manuscript. S.K. is grateful to Joanna Drążkowska and Tim Lichtenberg for sharing and discussing the solar system model in Figure 2. S.K. and T.K. acknowledge support from Science and Technology Facilities Council grant ST/Y002415/1. A.B. acknowledges support from JWST-GO-01640. K.Z. acknowledges support from JWST-GO-01584. This project was partially supported by the STScI grant JWST-GO01584 “A DSHARP-MIRI Treasury survey of Chemistry in Planet-forming Regions”. P.P. acknowledges funding from the UK Research and Innovation (UKRI) under the UK government’s Horizon Europe funding guarantee from ERC (under grant agreement No. 101076489). Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). This work benefited from information exchange within the program “Alien Earths” (NASA grant No. 80NSSC21K0593) for NASA’s Nexus for Exoplanet System Science (NExSS) research coordination network. The JWST data presented in this Letter were obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute. The specific observations analyzed can be accessed via doi:10.17909/cgfc-jx37.

Facilities

JWST - James Webb Space Telescope (MIRI), ALMA - Atacama Large Millimeter Array.

Software References

astropy (Astropy Collaboration et al. 2013, 2018, 2022), iSLAT (E. G. Jellison et al. 2024; M. Johnson et al. 2024).

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Additional details

Related works

Is new version of
Discussion Paper: arXiv:2508.10402 (arXiv)
Is supplemented by
Dataset: 10.17909/cgfc-jx37 (DOI)

Funding

Science and Technology Facilities Council
ST/Y002415/1
Space Telescope Science Institute
JWST-GO-01640
Space Telescope Science Institute
JWST-GO-01584
UK Research and Innovation
European Research Council
101076489
National Aeronautics and Space Administration
80NM0018D0004
National Aeronautics and Space Administration
80NSSC21K0593

Dates

Accepted
2025-08-13
Available
2025-09-10
Published

Caltech Custom Metadata

Caltech groups
Division of Geological and Planetary Sciences (GPS)
Publication Status
Published