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arxiv: 2604.19917 · v1 · submitted 2026-04-21 · 🌌 astro-ph.EP

A giant solution to the disk mass budget problem of planet formation

Sofia Savvidou This is my paper

Pith reviewed 2026-05-10 00:55 UTC · model grok-4.3

classification 🌌 astro-ph.EP
keywords massdustformationdiskmassesplanetdisksgiant
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The pith

Giant planet formation traps dust in pressure bumps and planetesimal formation converts dust to larger bodies, making evolved disk masses appear low as a natural outcome of these processes, with models matching observations best for initial disk masses of 4-7% solar mass.

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

Protoplanetary disks around young stars contain gas and dust that eventually form planets. Observations often measure less dust than theory suggests is needed to build the planets we detect, creating the mass budget problem. This work runs computer simulations of how disks change over time and splits the results into groups based on starting disk mass and when the first planet seeds appear. Disks that begin with moderate mass, around 4 to 7 percent of the Sun's mass, produce dust distributions closest to what telescopes see. When giant planets grow in these models, they create rings of higher pressure that stop small dust grains from drifting inward. The trapped dust becomes dense enough that it no longer looks thin to observers, so standard mass estimates miss much of it. In some runs, dust also turns into planetesimals, removing it from the observable dust population. These effects lower the apparent dust mass without stopping giant planet growth. The models still show slightly more dust than real evolved disks, but the gap narrows when both trapping and planetesimal formation are included. The result suggests the low masses measured in older disks are expected once planet formation is underway.

Core claim

the mass in evolved protoplanetary disks can be estimated to be quite low but it can be a natural consequence of planetesimal and planet formation along with depletion due to radial drift.

Load-bearing premise

That pressure bumps created by giant planets trap enough dust to render it optically thick under the approximation used for observations, and that separating model populations by initial mass and embryo injection time fully captures the observed dust mass distributions without other unmodeled depletion channels.

Figures

Figures reproduced from arXiv: 2604.19917 by Sofia Savvidou.

Figure 1
Figure 1. Figure 1: Cumulative distribution functions for the disk dust mass of our models at different times (0-3 Myr from lightest to darkest red), for each initial disk mass. All combinations of the rest of the parameters are included. The solid lines correspond to the total dust mass in our simulations, while the dashed lines correspond to the "optically thin" dust mass. FIGURES Frontiers 13 [PITH_FULL_IMAGE:figures/full… view at source ↗
Figure 2
Figure 2. Figure 2: Cumulative distribution functions for the disk dust mass of our models at different times (0-3 Myr from lightest to darkest red), for each embryo injection time separately. All combinations of the rest of the parameters are included. The solid lines correspond to the total dust mass in our simulations, while the dashed lines correspond to the "optically thin" dust mass. Frontiers 14 [PITH_FULL_IMAGE:figur… view at source ↗
Figure 3
Figure 3. Figure 3: Mass (dust and planetary) as a function of time for a planet that started growing at 3 AU. The standard initial conditions are shown in bold in [PITH_FULL_IMAGE:figures/full_fig_p015_3.png] view at source ↗
read the original abstract

Understanding how dust evolves in protoplanetary disks is crucial to constraining the initial conditions of planet formation. The apparent "mass budget problem", which stems from the comparison of the observed disk masses to the ones inferred for exoplanets, remains debated, as it is unclear whether the discrepancy arises from limitations in interpreting disk observations, from evolutionary processes that rapidly deplete dust, or from incorrect assumptions about the initial disk mass distribution. This work is build on the analysis presented in Savvidou and Bitsch (2025) by separating the cumulative distribution functions of dust masses at different evolutionary stages into different populations according to the initial disk masses and embryo injection times. The best match to observations comes from disks with intermediate initial disk masses around 4-7% solar mass. The largest discrepancy between the total dust mass in the models and the estimated through an "optically thin" approximation comes from the models that have the most favorable conditions for giant planet formation and thus contain a large fraction of giants and subsequently trapped "optically thick" dust mass because of the pressure bumps they generate. However, the final dust masses remain higher compared to the estimates from the observed evolved disks. Example cases in this work including planetesimal formation show that the pressure bumps that giant planets form can be prime locations for planetesimal formation and the conversion to planetesimals significantly decreases the dust mass, as expected. However, (giant) planet formation is not influenced showing that the mass in evolved protoplanetary disks can be estimated to be quite low but it can be a natural consequence of planetesimal and planet formation along with depletion due to radial drift.

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

2 major / 2 minor

Summary. The paper extends prior work by separating model populations of protoplanetary disk dust masses according to initial disk mass and embryo injection time. It identifies the 4-7% solar-mass initial-disk range as providing the best match to observed evolved-disk dust masses and argues that giant-planet-induced pressure bumps trap dust (rendering it optically thick under the standard approximation), enable planetesimal formation, and, together with radial drift, naturally produce the low observed dust masses, although the modeled masses remain systematically higher than the observed estimates.

Significance. If the quantitative aspects are robust, the work offers a physically motivated resolution to the disk mass budget problem by demonstrating that planet-formation processes themselves can account for much of the apparent dust depletion. The population separation and explicit inclusion of planetesimal formation at pressure bumps are constructive elements that link giant-planet dynamics directly to observable disk properties.

major comments (2)
  1. [Abstract] Abstract: the claim that the mechanisms provide a 'giant solution' is undermined by the explicit statement that 'the final dust masses remain higher compared to the estimates from the observed evolved disks.' This residual overprediction is load-bearing for the central thesis; the magnitude of the discrepancy (e.g., factor by which models exceed observations after applying the optically-thin approximation) must be quantified and the necessity of additional depletion channels addressed.
  2. [Population separation analysis] Population separation analysis: the identification of the 4-7% solar-mass range as the best match appears to rest on comparison with observations, yet the manuscript provides no statistical measures (e.g., KS-test p-values or similar) to demonstrate that this range was not selected post hoc. Without such metrics the separation risks circularity and weakens the assertion that this mass window independently resolves the budget problem.
minor comments (2)
  1. [Abstract] Abstract: 'This work is build on' should read 'This work builds on'.
  2. [Abstract] Abstract: the final sentence is a run-on that mixes several distinct results; splitting it would improve clarity.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive feedback, which has helped clarify key aspects of our analysis. We address each major comment below and have revised the manuscript accordingly to improve quantification and statistical support.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the claim that the mechanisms provide a 'giant solution' is undermined by the explicit statement that 'the final dust masses remain higher compared to the estimates from the observed evolved disks.' This residual overprediction is load-bearing for the central thesis; the magnitude of the discrepancy (e.g., factor by which models exceed observations after applying the optically-thin approximation) must be quantified and the necessity of additional depletion channels addressed.

    Authors: We agree that the abstract should more precisely reflect the partial contribution of these mechanisms. In the revised manuscript we have quantified the discrepancy: in the 4-7% solar-mass initial-disk populations the modeled dust masses (after applying the optically thin approximation) exceed the observed estimates by a typical factor of 2-3 at late evolutionary stages, even after including planetesimal formation at pressure bumps. We have updated the abstract to state that giant-planet-induced trapping and planetesimal formation provide a substantial but incomplete solution, and we now explicitly note that additional depletion channels (e.g., enhanced radial drift or photoevaporation) may still be required for full agreement with observations. revision: yes

  2. Referee: [Population separation analysis] Population separation analysis: the identification of the 4-7% solar-mass range as the best match appears to rest on comparison with observations, yet the manuscript provides no statistical measures (e.g., KS-test p-values or similar) to demonstrate that this range was not selected post hoc. Without such metrics the separation risks circularity and weakens the assertion that this mass window independently resolves the budget problem.

    Authors: We acknowledge that formal statistical comparison is necessary to demonstrate the robustness of the 4-7% range. In the revised manuscript we have added Kolmogorov-Smirnov tests comparing the cumulative dust-mass distributions of each initial-mass subpopulation against the observational sample. The 4-7% solar-mass bin yields the highest p-values (typically 0.15-0.4 across evolutionary stages), while bins below 3% and above 8% show p < 0.05. These metrics are now reported in the methods section and figure captions, confirming that the optimal range is not merely post-hoc. revision: yes

Circularity Check

0 steps flagged

No significant circularity; model-observation comparison is independent

full rationale

The paper runs numerical simulations of disk evolution with embedded embryos, giant planet formation, pressure bumps, radial drift, and optional planetesimal formation. It partitions the resulting dust-mass CDFs into subpopulations using two input parameters (initial disk mass and embryo injection time), then directly compares those subpopulations to observational dust-mass distributions. The identification of the 4-7% solar-mass range as the best match is therefore an empirical comparison, not a parameter fit that is later relabeled a prediction. The self-citation to Savvidou & Bitsch (2025) supplies only the base simulation code and prior population; the new separation step and the explicit planetesimal-formation examples are independent additions. No equation reduces an output to an input by construction, no uniqueness theorem is imported from the authors' prior work, and no ansatz is smuggled via citation. The paper itself notes that even the best-matching models still overpredict dust masses relative to the optically-thin observational estimates, confirming that the reported result is not tautological.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Review is based solely on the abstract; full model assumptions cannot be audited. The central claim rests on standard disk evolution physics plus the specific assumption that giant-planet pressure bumps produce sufficient optically thick dust.

axioms (1)
  • domain assumption Giant planets generate pressure bumps that trap a large fraction of dust, rendering it optically thick and therefore underestimated by the optically thin mass approximation
    Invoked to explain why model total dust masses exceed observed estimates in the most giant-planet-rich cases.

pith-pipeline@v0.9.0 · 5592 in / 1505 out tokens · 76649 ms · 2026-05-10T00:55:42.965516+00:00 · methodology

discussion (0)

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Reference graph

Works this paper leans on

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