Linking stellar composition to the nature and mass fraction of ice and organic compounds in exo-ocean worlds
Abstract
The elemental composition of planets is tightly linked to that of their host stars. Planets formed beyond the soot and snow lines may accrete reservoirs composed of ices and refractory organic compounds, making them potential candidates for ocean worlds. We combine stellar spectroscopy and planetary interior models to investigate how metallicity and elemental ratios (Mg/Si, C/Si, O/Si, Fe/Si) shape the rocky, ice-rich, and organic-rich building blocks available to small exoplanets (R < 2 R ⊕ , M < 10 M ⊕ ) around G-, K-, and M-type stars. Our results reveal a metallicity-driven transition from ice-rich building blocks around metal-poor stars to increasingly organic-rich reservoirs around metal-rich stars, while the rocky component remains comparatively stable. By comparing stellar-derived building-block inventories with exoplanet mass–radius observations for a limited sample of 18 stars hosting 26 small exoplanets (all with measured O, C, Mg, Si, and Fe abundances), we establish a first-order Δ R − X i c e diagnostic that identifies which planets are most consistent with formation beyond the snow line and retention of primordial ice-rich material. In our sample, six planets lie close to stellar-derived expectations, broadly consistent with formation beyond the snow line followed by inward migration. Ice- and organic-rich interiors may generate distinct secondary atmospheric signatures. As atmospheric surveys expand with JWST and ARIEL, this stellar abundance-based framework provides a testable, predictive basis for identifying and interpreting worlds formed beyond the soot and snow lines.
Related
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BibTeX
@article{decocq2026linking,
title = {{Linking stellar composition to the nature and mass fraction of ice and organic compounds in exo-ocean worlds}},
author = {Emeline Decocq and Mathilde Kervazo and Christophe Sotin},
journal = {Icarus},
year = {2026},
month = sep,
doi = {10.1016/j.icarus.2026.117309},
url = {https://hal.science/hal-05743786v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Linking stellar composition to the nature and mass fraction of ice and organic compounds in exo-ocean worlds
AU - Emeline Decocq
AU - Mathilde Kervazo
AU - Christophe Sotin
PY - 2026
DA - 2026/09/09
JO - Icarus
DO - 10.1016/j.icarus.2026.117309
UR - https://hal.science/hal-05743786v1
AB - The elemental composition of planets is tightly linked to that of their host stars. Planets formed beyond the soot and snow lines may accrete reservoirs composed of ices and refractory organic compounds, making them potential candidates for ocean worlds. We combine stellar spectroscopy and planetary interior models to investigate how metallicity and elemental ratios (Mg/Si, C/Si, O/Si, Fe/Si) shape the rocky, ice-rich, and organic-rich building blocks available to small exoplanets (R < 2 R ⊕ , M < 10 M ⊕ ) around G-, K-, and M-type stars. Our results reveal a metallicity-driven transition from ice-rich building blocks around metal-poor stars to increasingly organic-rich reservoirs around metal-rich stars, while the rocky component remains comparatively stable. By comparing stellar-derived building-block inventories with exoplanet mass–radius observations for a limited sample of 18 stars hosting 26 small exoplanets (all with measured O, C, Mg, Si, and Fe abundances), we establish a first-order Δ R − X i c e diagnostic that identifies which planets are most consistent with formation beyond the snow line and retention of primordial ice-rich material. In our sample, six planets lie close to stellar-derived expectations, broadly consistent with formation beyond the snow line followed by inward migration. Ice- and organic-rich interiors may generate distinct secondary atmospheric signatures. As atmospheric surveys expand with JWST and ARIEL, this stellar abundance-based framework provides a testable, predictive basis for identifying and interpreting worlds formed beyond the soot and snow lines.
SN - 0019-1035
SN - 1090-2643
ER -