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arxiv: 2606.20464 · v1 · pith:MPIVQ2NBnew · submitted 2026-06-18 · 🌌 astro-ph.EP

Atmospheric diversity of sub-Neptunes from formation with rock, water, and soot

Caroline Dorn , Aaron Werlen , Sean Jordan This is my paper

Pith reviewed 2026-06-26 15:32 UTC · model grok-4.3

classification 🌌 astro-ph.EP
keywords sub-Neptunesatmospheric compositionformation modelsexoplanet atmospheresJWST observationschemical equilibriumH2O/CH4 ratiomean molecular weight
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The pith

Sub-Neptune atmospheres carry chemical fingerprints of their rock, water, and soot building blocks that the H2O/CH4 ratio and mean molecular weight can diagnose together.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper models sub-Neptunes assembled from different proportions of rock, water, and refractory carbon to compute their interior and atmospheric compositions under global chemical equilibrium. Water-poor formation produces atmospheres depleted in carbon species with log(CH4) and log(CO2) below -4, while water-rich formation yields methane- and CO2-rich atmospheres with higher metal mass fractions and C/O ratios. Soot further boosts methane and can produce methane-dominated cases. The H2O/CH4 ratio paired with mean molecular weight serves as a two-dimensional diagnostic that ties observed composition to formation location inside or outside the water ice line. JWST data on K2-18b and TOI-270d fit water-rich formation without soot, while TOI-421b and GJ3470b fit water-poor formation.

Core claim

Planets formed from water-poor material produce atmospheres strongly depleted in carbon-bearing species, with log(CH4) and log(CO2) below -4. Planets assembled from water-rich building blocks naturally develop methane- and carbon-dioxide-rich atmospheres with elevated metal mass fractions and C/O ratios. The presence of refractory carbon further enhances methane production and can lead to methane-dominated atmospheres. The ratio H2O/CH4 combined with the mean molecular weight provides a two-dimensional diagnostic linking atmospheric composition to formation environment, with departures explained by water condensation or fractionated mass loss.

What carries the argument

The two-dimensional diagnostic of the H2O/CH4 ratio together with mean molecular weight that maps observed atmospheric composition back to the initial proportions of rock, water, and soot.

If this is right

  • Water-rich formation without soot explains the atmospheres of K2-18b and TOI-270d.
  • Water-poor formation inside the water ice line matches TOI-421b and GJ3470b.
  • Soot in the building blocks further increases methane and can produce methane-dominated atmospheres.
  • Departures from the main trends arise from water condensation in temperate cases or fractionated atmospheric mass loss.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The diagnostic could be tested on additional JWST targets to map formation locations across the sub-Neptune population.
  • If core-envelope mixing proves common, it would weaken the direct mapping from observed ratios to initial building-block proportions.
  • The framework predicts specific C/O ratio ranges that future high-precision spectroscopy could check against formation models.

Load-bearing premise

The final atmospheric composition is set only by the initial proportions of rock, water, and soot under global chemical equilibrium, without dominant post-formation processes such as core-envelope mixing or atmospheric escape changing the link.

What would settle it

A sub-Neptune observation where the measured H2O/CH4 ratio and mean molecular weight fall outside the ranges predicted for any combination of rock, water, and soot fractions, after accounting for condensation or mass loss.

Figures

Figures reproduced from arXiv: 2606.20464 by Aaron Werlen, Caroline Dorn, Sean Jordan.

Figure 1
Figure 1. Figure 1: Considered bulk core compositions. Core material excludes priordial H-dominated gas and encompasses all planet building material that is accreted in condensed form. Figure is adapted from (Li et al. 2026). 0.02 0.04 0.06 0.08 accreted mprimordial/Mp 10 4 10 3 10 2 10 1 100 101 Atmospheric C/O (a) 0.02 0.04 0.06 0.08 accreted mprimordial/Mp 10 2 10 1 Atmospheric mass fraction ( b ) 0.02 0.04 0.06 0.08 accre… view at source ↗
Figure 2
Figure 2. Figure 2: Atmospheric properties of the four modeled planet cases after chemical equilibration: (a) atmospheric C/O ratio, (b) atmospheric mass fraction, (c) atmospheric metal mass fraction Z, and (d) mean molecular weight (MMW). The volatile-rich cases (3 and 4) display markedly higher atmospheric C/O ratios and metal mass fractions than the volatile-poor cases (1 and 2). Case 3 also exhibits an atmospheric mass fr… view at source ↗
Figure 3
Figure 3. Figure 3: Molar mixing ratios of atmospheric species in equilibrium with the underlying magma ocean. Although the gas composition depends only weakly (to second order) on the fraction of accreted primordial gas, it varies substantially among the four cases. In cases 1 and 2, the atmosphere is dominated by H2 and H2O, whereas case 3 is characterized by CH4, CO, and H2, and case 4 by H2, CH4, and H2O. straints are giv… view at source ↗
Figure 4
Figure 4. Figure 4: Atmospheric profiles connecting the AMOI interface with the upper observable part of the atmosphere. Profiles are shown for the soot-rock case 2 (left), the soot-water-rock case 3 (middle), and the water-rock case 4 (right). Top: Pressure–temperature profiles before and after convergence. Middle: Vertical mixing ratio profiles of the considered gas species. Bottom: Vertical profiles of MMW. Here, we consid… view at source ↗
Figure 5
Figure 5. Figure 5: Molar mixing ratios of CH4/H2O versus mean molecular weight (MMW) as a diagnostic of sub-Neptune formation location - together with inferred atmospheric characteristics of sub-Neptunes from JWST data. Right: Model predictions for all four core composition cases across variations in TAMOI, showing how volatile-poor (cases 1 and 2) and volatile-rich (cases 3 and 4) formation scenarios occupy distinct regions… view at source ↗
read the original abstract

Recent JWST detections of CH4 and CO2 in sub-Neptune atmospheres point to a link between atmospheric composition and the nature of planetary building blocks - rock, water, or refractory carbon ("soot") - yet this connection remains poorly understood. Here we investigate how different formation environments shape the coupled interior and atmospheric compositions of sub-Neptunes. We model planets assembled from varying proportions of rock, water, and soot and compute the global chemical equilibrium and the overlying atmospheric structure. We find that planets formed from water-poor material produce atmospheres strongly depleted in carbon-bearing species, with log(CH4) and log(CO2) below -4. In contrast, planets assembled from water-rich building blocks naturally develop methane- and carbon-dioxide-rich atmospheres with elevated metal mass fractions and C/O ratios. The presence of refractory carbon (soot) further enhances methane production and can lead to methane-dominated atmospheres. Comparison with JWST observations suggests that water-rich formation is sufficient to explain K2-18b and TOI-270d with no soot component required, while TOI-421b and GJ3470b are consistent with water-poor formation inside the water ice line. The ratio H2O/CH4 combined with the mean molecular weight (MMW) provides a powerful two-dimensional diagnostic linking atmospheric composition to formation environment, with departures from the predicted trends explained by water condensation in temperate atmospheres or fractionated atmospheric mass loss.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 0 minor

Summary. The manuscript models sub-Neptunes assembled from varying proportions of rock, water, and soot building blocks, computes global chemical equilibrium compositions and atmospheric structures, and concludes that water-rich formation produces CH4/CO2-rich atmospheres with elevated metal fractions while water-poor formation yields carbon-depleted atmospheres. It proposes the H2O/CH4 ratio combined with mean molecular weight as a two-dimensional diagnostic linking atmospheric properties to formation environment and matches specific JWST targets (K2-18b and TOI-270d to water-rich; TOI-421b and GJ3470b to water-poor), attributing departures to condensation or fractionated loss.

Significance. If the formation-to-atmosphere mapping holds, the work supplies a concrete interpretive framework for JWST sub-Neptune spectra that directly ties observed molecular ratios and MMW to initial building-block proportions, which would be a useful advance for the field. The systematic variation of rock/water/soot fractions and the explicit two-dimensional diagnostic are positive features.

major comments (1)
  1. [Comparison with JWST observations] The central claim that the H2O/CH4–MMW diagnostic reliably links observed atmospheres to formation conditions rests on the assumption that post-formation processes (core-envelope mixing, energy-limited escape with fractionation) remain sub-dominant. The abstract notes that departures can be explained by condensation or fractionated loss, yet no quantitative assessment is given of how these processes would displace the model loci for the matched planets (K2-18b, TOI-270d, TOI-421b, GJ3470b). This is load-bearing for the diagnostic's applicability.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their constructive feedback and for recognizing the potential value of the H2O/CH4–MMW diagnostic. We address the single major comment below and agree that additional quantitative analysis is warranted.

read point-by-point responses

  1. Referee: The central claim that the H2O/CH4–MMW diagnostic reliably links observed atmospheres to formation conditions rests on the assumption that post-formation processes (core-envelope mixing, energy-limited escape with fractionation) remain sub-dominant. The abstract notes that departures can be explained by condensation or fractionated loss, yet no quantitative assessment is given of how these processes would displace the model loci for the matched planets (K2-18b, TOI-270d, TOI-421b, GJ3470b). This is load-bearing for the diagnostic's applicability.

    Authors: We agree that the lack of quantitative assessment of post-formation processes is a limitation for the robustness of the diagnostic. The manuscript currently provides only qualitative attribution of departures to condensation or fractionated loss. In revision we will add order-of-magnitude calculations (drawing on published escape and condensation models) showing how these processes would displace the loci of K2-18b, TOI-270d, TOI-421b and GJ3470b in the H2O/CH4–MMW plane, thereby testing whether the formation-environment interpretation remains viable. revision: yes

Circularity Check

0 steps flagged

No significant circularity; forward models derive diagnostic from explicit inputs

full rationale

The paper varies rock/water/soot proportions as explicit inputs, applies standard chemical equilibrium to compute atmospheric compositions and structures, and extracts the H2O/CH4–MMW trend as an emergent model result. No step reduces an output to a fitted parameter or self-citation by construction; the diagnostic is presented as a consequence of the forward modeling rather than presupposed. Assumptions about sub-dominant post-formation processes are stated openly but do not create definitional circularity. The derivation chain remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

Abstract-only review provides limited visibility into parameters and assumptions; the central claim rests on the choice of building-block proportions and the assumption of global chemical equilibrium.

free parameters (1)
  • proportions of rock, water, and soot
    Varying fractions are used as inputs to generate different formation scenarios; exact values or fitting procedure not stated in abstract.
axioms (1)
  • domain assumption Global chemical equilibrium determines the coupled interior and atmospheric compositions
    Invoked to compute CH4, CO2, and metal mass fractions from the initial building-block mix.

pith-pipeline@v0.9.1-grok · 5789 in / 1406 out tokens · 21276 ms · 2026-06-26T15:32:08.433856+00:00 · methodology

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Works this paper leans on

66 extracted references · 55 canonical work pages · 4 internal anchors

  1. [1]

    2025, The As- trophysical Journal, 985, L10, doi:10.3847/2041-8213/add010

    Ahrer, E.-M., Radica, M., Piaulet-Ghorayeb, C., et al. 2025, The As- trophysical Journal, 985, L10, doi:10.3847/2041-8213/add010

    work page doi:10.3847/2041-8213/add010 2025

  2. [2]

    E., Bergin, E

    Anderson, D. E., Bergin, E. A., Blake, G. A., et al. 2017, The Astro- physical Journal, 845, 13, doi:10.3847/1538-4357/aa7da1

    work page doi:10.3847/1538-4357/aa7da1 2017

  3. [3]

    P., Piet, H., Siebert, J., & Ryerson, F

    Badro, J., Brodholt, J. P., Piet, H., Siebert, J., & Ryerson, F. J. 2015, Proceedings of the National Academy of Sciences, 112, 12310, doi:10.1073/pnas.1505672112

    work page doi:10.1073/pnas.1505672112 2015

  4. [4]

    G., Welbanks, L., Schlawin, E., et al

    Beatty, T. G., Welbanks, L., Schlawin, E., et al. 2024, The Astrophys- ical Journal Letters, 970, L10, doi:10.3847/2041-8213/ad55e9

    work page doi:10.3847/2041-8213/ad55e9 2024

  5. [5]

    2024, arXiv e-prints, arXiv:2403.03227, doi:10.48550/arXiv.2403

    Benneke, B., Roy, P.-A., Coulombe, L.-P., et al. 2024, JWST Reveals CH4, CO2, and H2O in a Metal-rich Miscible Atmosphere on a Two-Earth-Radius Exoplanet, arXiv, doi:10.48550/arXiv.2403. 03325

    work page doi:10.48550/arxiv.2403 2024

  6. [6]

    I., Crockett, N., & Blake, G

    Bergin, E., Cleeves, L. I., Crockett, N., & Blake, G. 2014, Faraday Discussions, 168, 61, doi:10.1039/C4FD00003J

    work page doi:10.1039/c4fd00003j 2014

  7. [7]

    A., Blake, G

    Bergin, E. A., Blake, G. A., Ciesla, F., Hirschmann, M. M., & Li, J. 2015, Proceedings of the National Academy of Sciences, 112, 8965, doi:10.1073/pnas.1500954112

    work page doi:10.1073/pnas.1500954112 2015

  8. [8]

    A., Kempton, E

    Bergin, E. A., Kempton, E. M.-R., Hirschmann, M., et al. 2023, The Astrophysical Journal Letters, 949, L17, doi:10.3847/2041-8213/ acd377

    work page doi:10.3847/2041-8213/ 2023

  9. [9]

    C., Jennings, E

    Blanchard, I., Rubie, D. C., Jennings, E. S., et al. 2022, Earth and Planetary Science Letters, 580, 117374, doi:10.1016/j.epsl.2022. 117374

    work page doi:10.1016/j.epsl.2022 2022

  10. [10]

    J., Thompson, M

    Bower, D. J., Thompson, M. A., Hakim, K., Tian, M., & Sossi, P. A. 2025, Diversity of rocky planet atmospheres in the C-H-O-N-S-Cl system with interior dissolution, non-ideality, and condensation: Application to TRAPPIST-1e and sub-Neptunes, arXiv, doi:10. 48550/arXiv.2507.00499

    arXiv 2025

  11. [11]

    Burn, R., Bali, K., Dorn, C., Luque, R., & Grimm, S. L. 2024, Water- rich sub-Neptunes and rocky super Earths around different Stars: Radii shaped by Volatile Partitioning, Formation, and Evolution, arXiv, doi:10.48550/arXiv.2411.16879

    work page doi:10.48550/arxiv.2411.16879 2024

  12. [12]

    Chakrabarty, A., & Mulders, G. D. 2024, The Astrophysical Journal, 966, 185, doi:10.3847/1538-4357/ad3802

    work page doi:10.3847/1538-4357/ad3802 2024

  13. [13]

    M.-R., Nixon, M

    Davenport, B., Kempton, E. M.-R., Nixon, M. C., et al. 2025, ApJ, 984, L44, doi:10.3847/2041-8213/adcd76

    work page doi:10.3847/2041-8213/adcd76 2025

  14. [14]

    R., & Venturini, J

    Dorn, C., Hinkel, N. R., & Venturini, J. 2017, Astronomy & Astro- physics, 597, A38, doi:10.1051/0004-6361/201628749

    work page doi:10.1051/0004-6361/201628749 2017

  15. [15]

    2021, The Astrophysical Journal Letters, 922, L4, doi:10.3847/2041-8213/ac33af

    Dorn, C., & Lichtenberg, T. 2021, The Astrophysical Journal Letters, 922, L4, doi:10.3847/2041-8213/ac33af

    work page doi:10.3847/2041-8213/ac33af 2021

  16. [17]

    A., Cottrell, E., Hauri, E., Lee, K

    Fischer, R. A., Cottrell, E., Hauri, E., Lee, K. K. M., & Le Voyer, M. 2020, Proceedings of the National Academy of Sciences, 117, 8743, doi:10.1073/pnas.1919930117

    work page doi:10.1073/pnas.1919930117 2020

  17. [18]

    2026, Nature, 650, 60, doi:10.1038/ s41586-025-09970-4

    Gilmore, T., & Stixrude, L. 2026, Nature, 650, 60, doi:10.1038/ s41586-025-09970-4

    2026

  18. [19]

    2026, A New Global Chemical Equilibrium Code: Refractory Element Signatures in Super-Earths and Sub-Neptunes.https://arxiv.org/abs/2605

    Grimm, S., Steinmeyer, M.-L., Werlen, A., et al. 2026, A New Global Chemical Equilibrium Code: Refractory Element Signatures in Super-Earths and Sub-Neptunes.https://arxiv.org/abs/2605. 07833v1

    2026

  19. [20]

    L., Malik, M., Kitzmann, D., et al

    Grimm, S. L., Malik, M., Kitzmann, D., et al. 2021, The Astrophys- ical Journal Supplement Series, 253, 30, doi:10.3847/1538-4365/ abd773

    work page doi:10.3847/1538-4365/ 2021

  20. [21]

    2004, Geophysical Research Letters, 31, doi:10.1029/2003GL019380

    Hirao, N., Kondo, T., Ohtani, E., Takemura, K., & Kikegawa, T. 2004, Geophysical Research Letters, 31, doi:10.1029/2003GL019380

    work page doi:10.1029/2003gl019380 2004

  21. [22]

    Hirschmann, M. M. 2012, Earth and Planetary Science Letters, 341- 344, 48, doi:10.1016/j.epsl.2012.06.015

    work page doi:10.1016/j.epsl.2012.06.015 2012

  22. [23]

    2024, 683, L2, doi: 10.1051/0004-6361/202348238 16

    Holmberg, M., & Madhusudhan, N. 2024, Astronomy & Astrophysics, 683, L2, doi:10.1051/0004-6361/202348238

    work page doi:10.1051/0004-6361/202348238 2024

  23. [24]

    W., Vazan, A., Chariton, S., Prakapenka, V

    Horn, H. W., Vazan, A., Chariton, S., Prakapenka, V. B., & Shim, S.-H. 2025, Nature, 646, 1069, doi:10.1038/s41586-025-09630-7

    work page doi:10.1038/s41586-025-09630-7 2025

  24. [25]

    2025, A water-rich in- terior in the temperate sub-Neptune K2-18 b revealed by JWST, arXiv, doi:10.48550/arXiv.2507.12622

    Hu, R., Bello-Arufe, A., Tokadjian, A., et al. 2025, A water-rich in- terior in the temperate sub-Neptune K2-18 b revealed by JWST, arXiv, doi:10.48550/arXiv.2507.12622

    work page doi:10.48550/arxiv.2507.12622 2025

  25. [26]

    S., Fegley Jr., B., Schaefer, L., & Gaidos, E

    Kite, E. S., Fegley Jr., B., Schaefer, L., & Gaidos, E. 2016, The As- trophysical Journal, 828, 80, doi:10.3847/0004-637X/828/2/80

    work page doi:10.3847/0004-637x/828/2/80 2016

  26. [27]

    Krishnamurthy, V., Hirano, T., Gaidos, E., et al. 2023, Monthly No- tices of the Royal Astronomical Society, 521, 1210, doi:10.1093/ mnras/stad404 Article number, page 12 Caroline Dorn et al.: Atmospheric diversity of sub-Neptunes from formation with rock, water, and soot

    2023

  27. [28]

    2017, Astronomy & Astrophysics, 598, A98, doi:10.1051/0004-6361/201629140

    Leconte, J., Selsis, F., Hersant, F., & Guillot, T. 2017, Astronomy & Astrophysics, 598, A98, doi:10.1051/0004-6361/201629140

    work page doi:10.1051/0004-6361/201629140 2017

  28. [29]

    2024, A&A, 686, A131, doi:10.1051/0004-6361/202348928

    Leconte, J., Spiga, A., Clément, N., et al. 2024, A&A, 686, A131, doi:10.1051/0004-6361/202348928

    work page doi:10.1051/0004-6361/202348928 2024

  29. [30]

    Lee, E. K. H., Werlen, A., & Dorn, C. 2025, The Astrophysical Journal Letters, 990, L43, doi:10.3847/2041-8213/adfe62

    work page doi:10.3847/2041-8213/adfe62 2025

  30. [31]

    A., Hirschmann, M

    Li, J., Bergin, E. A., Hirschmann, M. M., et al. 2026, The Astrophys- ical Journal Letters, 997, L29, doi:10.3847/2041-8213/ae29a6

    work page doi:10.3847/2041-8213/ae29a6 2026

  31. [32]

    Li, Y., Vočadlo, L., Sun, T., & Brodholt, J. P. 2020, Nature Geo- science, 13, 453, doi:10.1038/s41561-020-0578-1

    work page doi:10.1038/s41561-020-0578-1 2020

  32. [33]

    2025, The Astrophysical Journal Letters, 990, L35, doi:10.3847/2041-8213/adfcc8

    Lin, Z., & Seager, S. 2025, The Astrophysical Journal Letters, 990, L35, doi:10.3847/2041-8213/adfcc8

    work page doi:10.3847/2041-8213/adfcc8 2025

  33. [34]

    Luo, H., Dorn, C., & Deng, J. 2024, Nature Astronomy, 8, 1399, doi:10.1038/s41550-024-02347-z Madhusudhan,N.,Sarkar,S.,Constantinou,S.,etal.2023,TheAstro- physical Journal Letters, 956, L13, doi:10.3847/2041-8213/acf577

    work page doi:10.1038/s41550-024-02347-z 2024

  34. [35]

    2017, Monthly Notices of the Royal Astronomical Society, 472, 447, doi:10.1093/mnras/stx1666

    Mahapatra, G., Helling, C., & Miguel, Y. 2017, Monthly Notices of the Royal Astronomical Society, 472, 447, doi:10.1093/mnras/stx1666

    work page doi:10.1093/mnras/stx1666 2017

  35. [36]

    M., et al

    Malik, M., Kitzmann, D., Mendonça, J. M., et al. 2019, The Astro- nomical Journal, 157, 170, doi:10.3847/1538-3881/ab1084

    work page doi:10.3847/1538-3881/ab1084 2019

  36. [37]

    M., et al

    Malik, M., Grosheintz, L., Mendonça, J. M., et al. 2017, The Astro- nomical Journal, 153, 56, doi:10.3847/1538-3881/153/2/56

    work page doi:10.3847/1538-3881/153/2/56 2017

  37. [38]

    2022, A&A, 665, A12, doi:10.1051/0004-6361/202243359

    Markham, S., Guillot, T., & Stevenson, D. 2022, A&A, 665, A12, doi:10.1051/0004-6361/202243359

    work page doi:10.1051/0004-6361/202243359 2022

  38. [39]

    D., et al

    Miozzi, F., Shahar, A., Young, E. D., et al. 2025, Nature, doi:10. 1038/s41586-025-09816-z

    2025

  39. [40]

    Misener, W., & Schlichting, H. E. 2022, Monthly Notices of the Royal Astronomical Society, 514, 6025, doi:10.1093/mnras/stac1732

    work page doi:10.1093/mnras/stac1732 2022

  40. [41]

    C., Somers, R

    Nixon, M. C., Somers, R. S., Savel, A. B., et al. 2025, The Astrophys- ical Journal, 995, 95, doi:10.3847/1538-4357/ae17c8

    work page doi:10.3847/1538-4357/ae17c8 2025

  41. [42]

    T., Mendonça, J

    Parker, L. T., Mendonça, J. M., Diamond-Lowe, H., et al. 2025, Lim- its on the atmospheric metallicity and aerosols of the sub-Neptune GJ 3090 b from high-resolution CRIRES+ spectroscopy, arXiv, doi:10.48550/arXiv.2503.16608

    work page doi:10.48550/arxiv.2503.16608 2025

  42. [43]

    A window for water-hydrogen demixing on warm metal-rich sub-Neptunes

    Piaulet-Ghorayeb, C., Thorngren, D. P., Kempton, E. M.-R., et al. 2025, A window for water-hydrogen demixing on warm metal-rich sub-Neptunes, arXiv, doi:10.48550/arXiv.2512.01805

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2512.01805 2025

  43. [44]

    Piaulet-Ghorayeb, C., Benneke, B., Radica, M., et al. 2024, ApJL, 974, L10, doi:10.3847/2041-8213/ad6f00 Rigby,F.E.,Madhusudhan,N.,Sarkar,S.,etal.2025,AJWSTTrans- missionSpectrumoftheTemperateSub-NeptuneTOI-732c,arXiv, doi:10.48550/arXiv.2512.15844

    work page doi:10.3847/2041-8213/ad6f00 2024

  44. [45]

    E., Pica-Ciamarra, L., Holmberg, M., et al

    Rigby, F. E., Pica-Ciamarra, L., Holmberg, M., et al. 2024, The As- trophysical Journal, 975, 101, doi:10.3847/1538-4357/ad6c38

    work page doi:10.3847/1538-4357/ad6c38 2024

  45. [46]

    Using observations of escaping H/He to constrain the atmospheric composition of sub-Neptunes

    Rogers, J. G., Owen, J. E., Schreyer, E., & Kirk, J. 2026, Using obser- vations of escaping H/He to constrain the atmospheric composition of sub-Neptunes, arXiv, doi:10.48550/arXiv.2601.14254

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2601.14254 2026

  46. [47]

    A., & Seager, S

    Rogers, L. A., & Seager, S. 2010, The Astrophysical Journal, 712, 974, doi:10.1088/0004-637X/712/2/974

    work page doi:10.1088/0004-637x/712/2/974 2010

  47. [48]

    2025, Nature Astronomy, 1, doi:10.1038/s41550-025-02723-3

    Roy, P.-A., Benneke, B., Fournier-Tondreau, M., et al. 2025, Nature Astronomy, 1, doi:10.1038/s41550-025-02723-3

    work page doi:10.1038/s41550-025-02723-3 2025

  48. [49]

    E., & Young, E

    Schlichting, H. E., & Young, E. D. 2022, The Planetary Science Jour- nal, 3, 127, doi:10.3847/PSJ/ac68e6

    work page doi:10.3847/psj/ac68e6 2022

  49. [50]

    P., MacDonald, R

    Schmidt, S. P., MacDonald, R. J., Tsai, S.-M., et al. 2025, The Astro- nomical Journal, 170, 298, doi:10.3847/1538-3881/ae019a

    work page doi:10.3847/1538-3881/ae019a 2025

  50. [51]

    2024, The Astrophysical Journal, 975, 14, doi:10.3847/1538-4357/ad7461

    Seo, C., Ito, Y., & Fujii, Y. 2024, The Astrophysical Journal, 975, 14, doi:10.3847/1538-4357/ad7461

    work page doi:10.3847/1538-4357/ad7461 2024

  51. [52]

    J., Ballmer, M

    Spaargaren, R. J., Ballmer, M. D., Bower, D. J., Dorn, C., & Tackley, P. J. 2020, Astronomy & Astrophysics, 643, A44, doi:10.1051/ 0004-6361/202037632

    2020

  52. [53]

    Steinmeyer, M.-L., Dorn, C., Werlen, A., & Grimm, S. L. 2026, Coupled thermal-chemical evolution models of sub-Neptunes re- veal atmospheric signatures of their formation location, arXiv, doi:10.48550/arXiv.2601.21377

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2601.21377 2026

  53. [54]

    W., Kitzmann, D., Patzer, A

    Stock, J. W., Kitzmann, D., Patzer, A. B. C., & Sedlmayr, E. 2018, Monthly Notices of the Royal Astronomical Society, doi:10.1093/ mnras/sty1531 Suárez-Andrés, L., Israelian, G., Hernández, J. I. G., et al. 2018, Astronomy & Astrophysics, 614, A84, doi:10.1051/0004-6361/ 201730743

    work page doi:10.1051/0004-6361/ 2018

  54. [55]

    2021, Nature Communi- cations, 12, 2588, doi:10.1038/s41467-021-22035-0

    Tagawa, S., Sakamoto, N., Hirose, K., et al. 2021, Nature Communi- cations, 12, 2588, doi:10.1038/s41467-021-22035-0

    work page doi:10.1038/s41467-021-22035-0 2021

  55. [56]

    2009, Geochimica et Cos- mochimica Acta Supplement, 73, A1321.https://ui.adsabs

    Terasaki, H., Ohtani, E., Sakai, T., et al. 2009, Geochimica et Cos- mochimica Acta Supplement, 73, A1321.https://ui.adsabs. harvard.edu/abs/2009GeCAS..73Q1321T/abstract

    2009

  56. [57]

    E., Wallack, N

    Teske, J., Batalha, N. E., Wallack, N. L., et al. 2025, JWST COM- PASS: NIRSpec/G395H Transmission Observations of TOI-776 c, a 2 Rearth M Dwarf Planet, arXiv, doi:10.48550/arXiv.2502.20501 Tsai,S.-M.,Lyons,J.R.,Grosheintz,L.,etal.2017,TheAstrophysical Journal Supplement Series, 228, 20, doi:10.3847/1538-4365/228/ 2/20

    work page doi:10.48550/arxiv.2502.20501 2025

  57. [58]

    Valatsou, M., Dorn, C., Marty, P., & Owen, J. E. 2026, The Astro- physical Journal, 1002, 53, doi:10.3847/1538-4357/ae5104

    work page doi:10.3847/1538-4357/ae5104 2026

  58. [59]

    M., Haldemann, J., Ronco, M

    Venturini, J., Guilera, O. M., Haldemann, J., Ronco, M. P., & Mor- dasini, C. 2020, A&A, 643, L1, doi:10.1051/0004-6361/202039141

    work page doi:10.1051/0004-6361/202039141 2020

  59. [60]

    L., Batalha, N

    Wallack, N. L., Batalha, N. E., Alderson, L., et al. 2024, The Astro- nomical Journal, 168, 77, doi:10.3847/1538-3881/ad3917

    work page doi:10.3847/1538-3881/ad3917 2024

  60. [61]

    2026a, The Role of Formation Location in Shaping Sulfur-, Nitrogen-, and Carbon- Bearing Species in Super-Earth and Sub-Neptune Atmospheres

    Werlen, A., Burn, R., Dorn, C., Felix, L., & Salmi, A. 2026a, The Role of Formation Location in Shaping Sulfur-, Nitrogen-, and Carbon- Bearing Species in Super-Earth and Sub-Neptune Atmospheres. https://arxiv.org/abs/2605.15170v1

    Pith/arXiv arXiv

  61. [62]

    2025a, The Astrophysical Jour- nal Letters, 991, L16, doi:10.3847/2041-8213/adff73

    Werlen, A., Dorn, C., Burn, R., et al. 2025a, The Astrophysical Jour- nal Letters, 991, L16, doi:10.3847/2041-8213/adff73

    work page doi:10.3847/2041-8213/adff73 2041

  62. [63]

    E., Grimm, S

    Werlen, A., Dorn, C., Schlichting, H. E., Grimm, S. L., & Young, E. D. 2025b, The Astrophysical Journal Letters, 988, L55, doi:10.3847/ 2041-8213/adf185

    2041

  63. [64]

    D., Shahar, A., & Schlichting, H

    Young, E. D., Shahar, A., & Schlichting, H. E. 2023, Nature, 616, 306, doi:10.1038/s41586-023-05823-0

    work page doi:10.1038/s41586-023-05823-0 2023

  64. [65]

    D., Stixrude, L., Rogers, J

    Young, E. D., Stixrude, L., Rogers, J. G., Schlichting, H. E., & Mar- cum, S. P. 2024, Planetary Science Journal, 5, 268, doi:10.3847/ PSJ/ad8c40

    2024

  65. [66]

    The Influences of Hydrogen-Silicate-Iron Miscibility on the Demographics of Sub-Neptunes and Super-Earths

    Young, E. D., & Werlen, A. 2026, The Influences of Hydrogen-Silicate- Iron Miscibility on the Demographics of Sub-Neptunes and Super- Earths, arXiv, doi:10.48550/arXiv.2604.28135

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2604.28135 2026

  66. [67]

    D., Werlen, A., Marcum, S

    Young, E. D., Werlen, A., Marcum, S. P., Stixrude, L., & Dullemond, C. P. 2025, The Planetary Science Journal, 6, 251, doi:10.3847/ PSJ/ae1012 Article number, page 13

    2025