{"id":"5e828348-688c-4d41-85ec-2e9f1fe1135c","arxiv_id":"2508.00980","paper_version":2,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"Dark matter annihilation energy deposited in planetary atmospheres and interiors, compared against existing UV airglow and heat flow measurements, yields new sub-GeV scattering constraints and long-lived mediator reach.","lead":"Using archival UV airglow and internal heat measurements of the Solar System planets, this paper derives new dark matter-nucleon scattering limits and shows different planets probe different dark matter masses and mediators. It turns existing planetary flyby data into a practical dark matter search, especially for light dark matter that conventional detectors miss.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"UV airglow limits count DM annihilation across the full 1 bar-to-exobase shell, but observable H2 Lyman-Werner emission only escapes from above the homopause; for sub-GeV heavy-mediator DM this may overestimate the UV signal by orders of magnitude.","rationale":"The reader's weakest assumption (the isothermal atmospheric DM profile, Eq. 9) is a legitimate uncertainty, but it is not the most load-bearing issue for the central claim. Even if the DM density profile is correct, the UV airglow signal requires that annihilation energy be converted into escaping H2 Lyman-Werner band photons. The manuscript's Eq. (30) and Eq. (34) count all annihilations in the geometric shell between the 1-bar radius and the exobase. In giant-planet atmospheres, the region that emits observable UV is the thermosphere above the homopause; at pressures near 1 bar the H2 column is optically thick and collisional quenching suppresses UV emission. The DM scale height at sub-GeV masses is only hundreds of km, so a large fraction of the annihilations counted in f_atm occur below the UV-emitting layer. The paper's stated justification—that the excitation threshold is low compared to annihilation energies—addresses the energy threshold but not the altitude/quenching problem. No radiative-transfer or energy-deposition-altitude calculation is presented for the heavy-mediator case. If this is corrected, the Jupiter/Saturn limits may weaken substantially; if the companion paper already performed such a calculation, the current paper should have used it rather than the geometric fraction. The concrete test will distinguish these cases. Because the headline conclusion rests on this unvalidated step, I recommend the paper be revised (or rejected as is) until the observable UV fraction is demonstrated to be comparable to f_atm.","tokens_in":32989,"tokens_out":32110,"duration_ms":414088,"concrete_test":"Recompute the heavy-mediator UV airglow constraints of Fig. 4 by replacing f_atm in Eq. (34) with the fraction of annihilation energy deposited above the homopause (P ≲ 1 μbar) using the actual H2 density profile and a simple energy-loss/radiative-transfer model for e± and photons from annihilation (or the companion paper's full deposition calculation if available). If the effective UV-producing fraction for mχ = 0.3-1 GeV is more than an order of magnitude below f_atm^heavy, the Fig. 4 UV limits weaken correspondingly and the Sec. V claim that planetary UV airglow surpasses direct detection for sub-GeV DM fails. A simpler diagnostic: compute f_atm with the upper limit of integration set to the homopause altitude instead of the exobase; if it drops by more than 10x for the mass range where the constraints beat direct detection, the concern is confirmed.","verdict_should_be":"REJECT","load_bearing_attack":"The central sub-GeV UV airglow claim (Sec. V, Fig. 4) assumes that every annihilation occurring between R (the 1-bar radius) and Ratm (exobase) contributes to the observed airglow with the same efficiency as precipitating auroral electrons. This is the assertion in Sec. II.B that 'effectively all of the annihilation energy is available to excite the molecules,' applied via Eq. (30) and the geometric fraction f_atm in Eq. (34). However, H2 Lyman and Werner band photons are absorbed by the overlying atmosphere below the homopause (pressure ~1 μbar) and are collisionally quenched at the high densities near 1 bar; observed nightside UV airglow originates in the thermosphere above the homopause. The DM atmospheric density falls with scale height H = kT(R)/(mχ g) (for Jupiter, mχ=0.3 GeV gives H~170 km), so the annihilation rate density falls as exp(-2h/H). For a homopause located ~400 km above 1 bar, only ~1% of the annihilation events counted in f_atm occur in the UV-transparent region at mχ=0.3 GeV; at 0.1 GeV the fraction is larger but still far below unity. The conversion factor 10 R/(µW/m^2) is calibrated for energy deposited in the emitting layer, not for energy released deep in the atmosphere. The manuscript contains no treatment of UV radiative transfer, quenching, or the altitude of energy deposition for the heavy-mediator scenario, so the headline 'more than 10%' refers to the geometric atmosphere, not to observable UV emission. If the correct fraction is orders of magnitude smaller, the Jupiter/Saturn limits in Fig. 4 no longer surpass direct detection.","agreement_with_reader":"disagree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper develops a general framework for interpreting dark matter energy injection in planets through two observables: UV airglow from the atmosphere and internal heat flow from the interior. It models DM capture, thermalization, annihilation, and evaporation, and computes the fraction of annihilation energy deposited in the atmosphere versus the interior for both a heavy (prompt) mediator and a light/long-lived mediator. These fractions are combined with published UV brightness and heat-flow measurements for Earth, Jupiter, Saturn, Uranus, and Neptune, as well as projections for a benchmark Super-Jupiter, to derive constraints on spin-independent and spin-dependent DM-nucleon scattering cross sections. The headline claim is that planetary UV airglow observations surpass direct detection limits for sub-GeV DM even with a heavy mediator, because a portion of the captured DM population annihilates in the atmosphere, and that planetary spectroscopy is therefore a powerful and complementary dark-sector probe.","tokens_in":33414,"tokens_out":4740,"duration_ms":62849,"significance":"If the central claims hold, the paper would establish a qualitatively new and competitive channel for sub-GeV DM-nucleon scattering, particularly for spin-dependent proton scattering where direct detection is weak. The framework is genuinely general: it treats radial DM profiles, mediator decay lengths, and planetary structure in a unified way, and the heavy- versus light-mediator comparison is a useful organizational principle. The authors make good use of existing public tools (Asteria) and public datasets, and they are careful to separate constraints from projections. However, the headline UV-airglow limits rest on an atmospheric emission model that is not developed in the paper, and several model-dependent ingredients (the atmospheric DM profile, the solar-calibrated transition parameters, and the evaporation cutoff) are adopted with only partial sensitivity testing. The paper is therefore valuable and likely correct in its broad architecture, but the quantitative sub-GeV limits require further support.","major_comments":[{"comment":"The UV airglow constraints count all annihilation events between the 1-bar radius R and the exobase Ratm through the fraction f_atm in Eq. (34), and impose Eq. (31) using a 10 R per uW/m2 conversion factor calibrated for precipitating electrons. However, H2 Lyman and Werner band photons are collisionally quenched and absorbed below the homopause, and the observed nightside UV airglow originates mainly above the homopause. The DM atmospheric density falls with scale height H = kT(R)/(m_chi g); for Jupiter at m_chi = 0.3 GeV this is roughly 170 km, while the homopause is typically a few hundred km above the 1-bar level. Thus only a small fraction of the events counted in f_atm occur in the UV-transparent region. The manuscript contains no radiative-transfer or quenching treatment and does not distinguish the energy deposition altitude from the emission altitude. This is a load-bearing issue for the central sub-GeV UV-airglow limits in Fig. 4, which may be overestimated by orders of magnitude. I ask the authors to either perform a vertical radiative-transfer estimate, conservatively restrict f_atm to the region above the homopause, or quantify the resulting reduction of the claimed limits.","section":"II.B, Eqs. (30)-(31), (34), and Fig. 4"},{"comment":"The atmospheric DM profile is assumed to be isothermal at the planetary surface temperature T(R), joined to the interior LTE profile at R and truncated at a mass-dependent radius Rmax given by Eq. (10). This assumption directly controls the atmospheric annihilation fraction and hence the 'more than 10% of captured DM annihilates in the atmosphere' claim in Sec. V. The paper notes that an alternative truncation changes results by only about 10%, but it does not quantify the sensitivity to the assumed profile shape, e.g., a depleted profile due to atmospheric winds or incomplete thermalization, or a different treatment of the exobase boundary. Because this is the key physical input that enables the sub-GeV airglow constraints, the authors should provide a sensitivity study over plausible atmospheric DM distributions and demonstrate that the headline limits are robust, or state the extent to which they weaken.","section":"I.B.3, Eqs. (9)-(10)"},{"comment":"The transition between the LTE and isothermal radial profiles is interpolated using f(K) with K0 = 0.4 and sigma = 0.5, parameters fitted to solar simulations [105]. The same functional form is applied to all planets, whose atmospheric compositions, temperatures, and Knudsen-number regimes differ substantially from the Sun. Since the cross-section limits in Fig. 4 span the intermediate regime where this blending matters, the authors should show the sensitivity of the constraints to the choice of K0 and sigma, for example by comparing the pure-LTE and pure-isothermal limits with the blended result. Without this, the robustness of the limits across the full cross-section range is not established.","section":"I.B.5, Eqs. (12)-(13)"},{"comment":"The low-mass reach of all the constraints is set by the evaporation cutoff, and the paper states that the evaporation smoothing changes results by 'a few tens of percent' and that varying the core temperature shifts the cutoff approximately linearly in DM mass. Since the headline sub-GeV sensitivity in Fig. 4 extends to masses near 0.1 GeV and below, the evaporation uncertainty directly affects the claimed region of new parameter space. I recommend displaying the evaporation mass cutoff as an uncertainty band, or explicitly quoting the range of cutoff masses for each planet under reasonable core-temperature variations, so that the reader can judge how much of the sub-GeV reach is robust.","section":"I.D, Eqs. (22)-(29)"}],"minor_comments":[{"comment":"The conversion factor of 10 R per uW/m2 is stated to be model-dependent, with values ranging from 7.8 to 14.6 R depending on electron energy. Since this factor enters all airglow limits linearly, its uncertainty should be propagated into the final constraints or quoted as a systematic band.","section":"II.A.1, Table I"},{"comment":"The Super-Jupiter is described as 'local free-floating' for the UV airglow projection but as located at 0.1 kpc from the Galactic Center for the internal-heating projection. These are different benchmarks with different DM densities and backgrounds; the text should state this explicitly to avoid confusion.","section":"II.A.3 and II.C.3"},{"comment":"The caption does not mention that Earth is omitted from the 0.5 GeV isothermal panel; the text explains this, but a short caption note would improve readability.","section":"Fig. 2"},{"comment":"The expression Rmax ~ GM m_chi / T_chi is dimensionally correct only in units where Boltzmann's constant is unity; this should be stated or written with k_B explicitly for clarity.","section":"I.B.3, Eq. (10)"},{"comment":"The notation Cann is used both as an annihilation rate coefficient in Eq. (1) and as the coefficient in Eq. (18); the two are related but distinct, and a brief clarifying sentence would help the reader track the dimensions.","section":"I.C, Eq. (17)"}],"recommendation":"major_revision","confidential_remarks":"The paper's framework and scope are well suited to the journal, and the authors have assembled a rich set of observations and model calculations. The main risk is the UV-airglow interpretation: the geometric atmospheric fraction is not the same as the observable emission fraction, and this affects the central sub-GeV limits. If the authors can add a radiative-transfer treatment or conservatively restrict the atmospheric emission region, I would be willing to support publication after a revised version. I would also encourage them to make the atmospheric DM profile sensitivity quantitative, since that is the other main pillar of the headline claim."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Two quick takeaways. First, the paper genuinely advances the planetary-DM program: the internal heat flow constraints, the radial energy-deposition framework, the displaced-mediator Monte Carlo, and the SD-neutron/subfraction results are all useful and mostly well executed. Second, the headline UV airglow constraints on sub-GeV DM have a serious potential flaw that the paper does not address.\n\nThe problem is altitude. The observed H2 Lyman-Werner nightside emission comes from above the homopause; below that, the atmosphere is optically thick and the UV photons are absorbed or quenched. But Eq. (30) assigns the full annihilation power from the 1-bar surface out to the exobase as if it all produced observable airglow. For a 0.3 GeV DM particle on Jupiter, the DM scale height in the atmosphere is ~170 km, and the homopause sits ~400 km up, so only about 1% of the annihilations counted in f_atm occur in the UV-transparent region. The 10 R per µW/m^2 conversion factor is calibrated for energy deposited in the emitting layer, not deep in the atmosphere. This is not a minor detail; it removes the factor that allows Jupiter and Saturn to beat direct detection in Fig. 4.\n\nThe internal heating constraints are on much firmer ground, since they don't care where below the surface the energy is deposited. The light-mediator deposition framework is carefully described and looks reproducible. I also appreciate the honest discussion of composition and advection uncertainties, and the self-citation to the companion paper is appropriate since that is where the UV airglow idea originates.\n\nThe model-dependent ingredients—the isothermal atmospheric density profile, the solar-fitted blending parameters, the evaporation cutoff—are secondary compared to the homopause issue, but they are worth sensitivity checks. And the plotted limits don't propagate the quoted observational uncertainties, which is a referee-level request, not a fatal flaw.\n\nWho should read this: anyone working on DM capture in celestial bodies, and planetary spectroscopists who want to see how their data are being used. I would send it to peer review, because the framework and the heating constraints are worth publishing, but the referee must insist on a proper treatment of the UV emitting layer, or a redefinition of f_atm to only count annihilations above the homopause. If the authors can show that the escaping UV or a related observable still tracks the deep annihilation power, the paper might stand; otherwise the airglow sections need major revision.","headline":"A genuinely useful framework for planetary DM energy deposition with a serious unaddressed problem in the UV airglow constraints: they count annihilation below the homopause that cannot contribute to the observed emission.","tokens_in":33901,"tokens_out":5049,"would_cite":false,"duration_ms":63797,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":["95.35.+d"],"model":"deepseek-v4-flash","headline":"Existing UV airglow measurements of Jupiter and Saturn could place the strongest current limits on sub-GeV dark matter scattering, even when annihilation goes through a heavy mediator.","keywords":["dark matter capture","planetary UV airglow","sub-GeV dark matter","internal heat flow","long-lived mediators","gas giant atmospheres","spin-dependent scattering"],"falsifier":"Run a full atmospheric simulation of the exobase region for Jupiter or Saturn, including vertical mixing, winds, and momentum transfer from dark matter scattering, and compare the steady-state captured dark matter density above the 1-bar surface with the isothermal extension of Eq. 9. If the atmosphere depletes the dark matter population by a factor of two or more, the headline sub-GeV airglow constraints weaken by the same factor; if the population survives, the constraints stand.","tokens_in":32769,"feed_emoji":"🪐","tokens_out":8680,"duration_ms":97979,"temperature":0.7,"pith_summary":"This paper argues that planets can act as dark matter detectors: dark matter that scatters off planetary material and is captured can annihilate, and the energy it injects shows up as ultraviolet nightglow from molecular hydrogen in the atmosphere or as excess heat flowing from the interior. The authors compare predicted annihilation power with existing UV airglow and internal heat measurements for Earth, the gas giants, the ice giants, and a hypothetical Super-Jupiter, and derive constraints on dark matter-nucleon scattering. Their headline result is that for sub-GeV dark matter annihilating through a heavy mediator, ultraviolet airglow limits from Jupiter and Saturn on both spin-independent and spin-dependent proton scattering surpass current direct detection limits, because a portion of the captured dark matter sits in the isothermal upper atmosphere and annihilates there. A sympathetic reader would care because this would mean the strongest current limits on the lightest dark matter masses come from planetary observations already in hand, not from new underground detectors.","feed_headline":"Gas-giant UV airglow beats direct detectors on light dark matter","feed_subtitle":"Existing Voyager and Cassini nightglow data on Jupiter and Saturn already constrain sub-GeV dark matter scattering","key_machinery":"The load-bearing quantity is the atmospheric annihilation fraction $f_{\\rm atm}$, the share of dark matter annihilation events that deposit energy in the atmosphere, defined through an integral over the squared normalized dark matter density profile $G_\\chi(r)$. The profile itself combines a local-thermal-equilibrium interior distribution with an isothermal atmospheric extension at the planet's surface temperature (Eq. 9), truncated at a mass-dependent radius $R_{\\rm max}$ (Eq. 10), with the two limiting regimes blended according to the Knudsen number, the ratio of the dark matter mean free path to its scale radius. This machinery makes the paper's central effect possible: light dark matter extends into the rarefied atmosphere, so a substantial fraction of captured particles annihilate there and produce UV airglow even when the mediator is heavy.","core_discovery":"The paper's central claim is that the energy injected by dark matter annihilation inside a planet can be separated into an atmospheric fraction and an interior fraction, computable from the dark matter radial profile, the planet's temperature and density structure, and the mediator's decay length, and that comparing these fractions with observed UV airglow and internal heat flow produces dark matter constraints. Even when annihilation goes through a heavy mediator, more than ten percent of captured sub-GeV dark matter annihilates in the atmosphere because a thermalized population resides in the upper atmosphere, which is treated as an isothermal layer at the planet's surface temperature. The resulting hydrogen Lyman and Werner band emission is bounded by Voyager and New Horizons nightglow data for the giant planets, giving Jupiter and Saturn the best current limits on spin-independent (scattering independent of nuclear spin) and spin-dependent proton (scattering on unpaired proton spin) interactions below about a GeV. For light, long-lived mediators, planets of different radii probe different decay lengths, so the ensemble of Earth, ice giants, and gas giants maps out mediator parameter space in a way that complements collider long-lived particle searches.","pith_inferences":["Beyond the paper: if the atmospheric dark matter population is partially depleted by winds, vertical mixing, or incomplete thermalization, the sub-GeV airglow limits would weaken approximately in proportion; atmospheric modelling of the exobase, the transition to the collisionless upper atmosphere, could quantify this.","Beyond the paper: the same capture-and-deposition machinery could be applied to hydrogen-rich brown dwarfs and mini-Neptunes with measured or modelable exobase temperatures, extending the mass and decay-length reach beyond the Solar System.","Beyond the paper: the conversion from brightness to precipitating power, about 10 Rayleigh per microwatt per square meter, is the single largest observational multiplier, so an improved empirical calibration of H2 Lyman and Werner band brightness versus electron power would shift all airglow limits by a common factor.","Beyond the paper: a latitudinally or time-resolved UV dataset could separate a dark matter airglow component from auroral and dayglow backgrounds, potentially turning the constraints reported here into a positive detection channel."],"forward_implications":["Existing Jupiter and Saturn UV nightglow data constrain sub-GeV dark matter-nucleon scattering more strongly than current direct detection experiments, so a first test of this mass range requires no new instrumentation.","The airglow channel opens parameter space for strongly interacting dark matter subcomponents that never reach underground detectors, and for spin-dependent neutron-only scattering that cosmology cannot constrain.","Planets of different radii are sensitive to different mediator decay lengths, so the Solar System ensemble and future Super-Jupiters map out light-mediator parameter space in a way that complements long-lived particle collider searches.","A free-floating Super-Jupiter could extend the same techniques: UV airglow observations project new sub-GeV sensitivity, and internal heat observations near the Galactic Center project sensitivity to large, previously untested cross sections.","Because the constraints depend only on total energy deposited, they are insensitive to branching ratios and spectral details of the annihilation products, which makes them applicable across many dark sector models."],"supporting_citations":[{"why":"the paper's companion study that introduced the UV airglow signature and supplied its original assumptions","marker":"[120]"},{"why":"supplies the Jupiter nightside UV airglow measurement used to set the airglow constraint","marker":"[153]"},{"why":"supplies the Saturn nightside UV airglow measurement used to set the airglow constraint","marker":"[155]"},{"why":"supplies the Uranus and Neptune nightside UV airglow measurements used for the ice giant constraints","marker":"[157]"},{"why":"supplies the Cassini Jupiter internal heat measurement used for the heating constraint","marker":"[154]"},{"why":"supplies the Cassini Saturn internal heat measurement used for the heating constraint","marker":"[156]"},{"why":"supplies the terrestrial borehole heat flow measurement used for the Earth heating constraint","marker":"[152]"},{"why":"supplies the blending of local-thermal-equilibrium and isothermal dark matter profiles used in the transition regime","marker":"[105]"},{"why":"supplies the capture-rate calculation that sets the number of captured dark matter particles across single- and multi-scatter regimes","marker":"[124]"},{"why":"supplies the diffusion and advection timescale comparison that delimits where the dark matter profile is unperturbed","marker":"[133]"}],"fun_headline_variants":["Gas-giant airglow pins down sub-GeV dark matter","Jupiter and Saturn airglow best sub-GeV dark matter limits","Planets as dark matter detectors: gas giants lead limits","Planetary spectroscopy: gas giants probe light dark matter"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The results assume captured dark matter in the atmosphere follows an isothermal distribution at the planet's surface temperature, truncated at a mass-dependent radius; if that atmospheric population is depleted by winds, incomplete thermalization, or a different boundary treatment, the airglow limits weaken in proportion to the lost annihilation fraction.","fun_headline_variants_meta":{"raw":{"variants":["Gas-giant airglow pins down sub-GeV dark matter","Jupiter and Saturn airglow best sub-GeV dark matter limits","Planets as dark matter detectors: gas giants lead limits","Planetary spectroscopy: gas giants probe light dark matter"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000492,"raw_usage":{"total_tokens":2410,"prompt_tokens":926,"completion_tokens":1484,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":542,"completion_tokens_details":{"reasoning_tokens":1413}},"tokens_in":542,"tokens_out":1484,"duration_ms":13378,"temperature":1.0,"reasoning_tokens":1413,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-06T05:55:10.372318+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run a full atmospheric simulation of the exobase region for Jupiter or Saturn, including vertical mixing, winds, and momentum transfer from dark matter scattering, and compare the steady-state captured dark matter density above the 1-bar surface with the isothermal extension of Eq. 9. If the atmosphere depletes the dark matter population by a factor of two or more, the headline sub-GeV airglow constraints weaken by the same factor; if the population survives, the constraints stand.","supporting_citations":[{"cited_title":"Calorimetric Detection of Dark Matter","cited_arxiv_id":"2208.05485","evidence_quote":"supplies the Saturn nightside UV airglow measurement used to set the airglow constraint"},{"cited_title":"Gold, Proc","cited_arxiv_id":null,"evidence_quote":"supplies the Cassini Saturn internal heat measurement used for the heating constraint"},{"cited_title":"A Composite Solution to the Neutron Bottle Anomaly","cited_arxiv_id":"2008.06061","evidence_quote":"supplies the terrestrial borehole heat flow measurement used for the Earth heating constraint"}],"review_version":1}