{"id":"bbabc8e5-0893-4726-9e36-15d454406e5d","arxiv_id":"2607.04275","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"An HSO2-based HSO photolysis cross-section prescription increases S8 aerosol abundances and spectral haze signatures relative to the HO2 default for G/K-star Archean-like planets.","lead":"Updated HSO UV-Visible cross sections, proxied from HSO2 rather than HO2, raise S8 aerosol abundances by up to four orders of magnitude in Archean-like atmospheres. This strengthens haze scattering and absorption features in transmission, emission and reflection spectra for planets around G- and K-type stars.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.5","headline":"No significant objection identified beyond the reader's already-flagged proxy transferability.","rationale":"The central claim is a well-scoped sensitivity result: inside Atmos + POSEIDON, under elevated SO2 and cool-troposphere Archean-like conditions, the longer-wavelength HSO2 proxy drives higher HSO photolysis, higher HS production, and therefore higher S8, producing stronger haze signatures for G/K hosts. The paper is transparent about the proxy nature of the data, the single-channel QY assumption, the temperature independence, and the restricted planetary scenarios. The reader's weakest_assumption correctly identifies the only condition that must still be verified experimentally; no deeper load-bearing flaw (e.g., an algebraic error, an unphysical boundary condition that silently forces the S8 jump, or a circular use of the same data) appears on close reading. Therefore the CONDITIONAL verdict and the accompanying caveats stand without adjustment.","tokens_in":19161,"tokens_out":522,"duration_ms":7445,"concrete_test":"Re-run the G-star case of Figure 3 (SO2 = 6e10 cm-2 s-1) after replacing the HSO2-derived cross sections with any newly available experimental or high-level ab-initio HSO absorption spectrum (same wavelength grid, same QY=1 for HS+O); if the tropospheric S8 mixing-ratio ratio (updated/default) falls below ~10, the order-of-magnitude spectral claim weakens.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The reader's weakest assumption already isolates the single load-bearing condition for the strongest claim: that truncated HSO2 UV-Vis cross sections (Lu et al. 2021) with QY=1 for the HS+O channel alone are a sufficiently faithful proxy that the reported S8 abundance jumps (up to ~4 orders of magnitude) and consequent spectral enhancements are physically meaningful rather than artefacts of the proxy choice. Sections 2.1.1–2.1.3 motivate the proxy via vibrational frequencies and Cs symmetry, truncate at the 466.1 nm SO–H quantum limit, and deliberately omit the second photolysis channel and any long-wavelength opacity tail. The paper itself treats the result as a sensitivity demonstration and supplies the data publicly. No additional internal inconsistency, circularity, or unacknowledged modelling error is required for the claim to hold inside the stated scenarios; the conditional character of the result is already correctly diagnosed.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The paper argues that HSO UV–Visible photolysis cross sections, currently unmeasured and routinely replaced by HO2 data, are a high-priority input for photochemical models of anoxic terrestrial atmospheres. Using functional-group and Cs point-group arguments, the authors adopt simulated HSO2 cross sections (Lu et al. 2021), truncate them at the 466.1 nm SO–H quantum limit, and assign a constant quantum yield of 1 solely for the HS+O channel. They then run the Atmos photochemical model for Archean-like N2–CO2–H2O atmospheres under elevated SO2 surface fluxes around FGK hosts and generate transmission, emission and reflection spectra with POSEIDON. Relative to the default HO2 prescription, the updated cross sections raise integrated HSO photolysis rates and increase tropospheric S8 abundances by up to four orders of magnitude for G- and K-type hosts, producing stronger haze scattering slopes and S8 absorption features near 12 and 21 µm. No sensitivity appears for F- or M-type hosts. The new prescription and scaling tests are released publicly.","tokens_in":19436,"tokens_out":1091,"duration_ms":9120,"significance":"If the proxy is even approximately faithful, the work supplies a concrete, falsifiable prioritization of HSO for laboratory or ab initio characterization and shows that an untested modelling assumption can alter predicted S8 haze signatures that future HWO/LIFE observations of G/K-star terrestrial planets may target. Strengths include a clean isolation of the cross-section input, tabulated boundary conditions, public data release, and explicit scaling tests that bound the effect of order-of-magnitude errors in the proxy magnitude. The result is therefore useful both as a sensitivity demonstration and as a guide for experimental effort, even while remaining conditional on the HSO2-to-HSO transferability.","major_comments":[{"comment":"Sections 2.1.1–2.1.3 and the abstract claim that the truncated HSO2 spectrum is a “more reliable representation of HSO photolysis than HO2.” The supporting evidence is limited to vibrational-frequency proximity and shared Cs symmetry; electronic spectra are not guaranteed to follow from these criteria. Because the central spectral claim (S8 enhancements of up to four orders of magnitude) rests entirely on this proxy, the manuscript should either (i) supply additional electronic-structure or literature support that the UV continuum of HSO2 is a reasonable stand-in for HSO, or (ii) rephrase the claim throughout as a pure sensitivity experiment whose absolute magnitude remains unvalidated until direct HSO data exist.","section":null},{"comment":"Section 2.1.3 deliberately omits the second photolysis channel (SO+H, quantum limit 466.1 nm) and any long-wavelength opacity tail beyond that limit, while forcing QY=1 exclusively for HS+O. The paper notes that this choice isolates the cross-section effect, yet the same section acknowledges that wavelength-dependent branching is physically motivated. Because HS production is the direct driver of the reported S8 increase (net pathway in §3.2), a short test that redistributes quantum yield between the two channels (or simply reports the fractional contribution of wavelengths longward of the HO2 cut-off) is needed to show that the order-of-magnitude S8 jump is not an artefact of the single-channel assumption.","section":null}],"minor_comments":[{"comment":"Figure 1 caption and §2.4: the M-dwarf spectrum is shown but never used in the main figures; a one-sentence pointer to the (null) M-dwarf result already stated in §4 would avoid reader confusion.","section":null},{"comment":"Table 1: the HSO2 reference is listed as F2019 but the bibliography entry is Fortenberry & Francisco 2021; align year and citation key.","section":null},{"comment":"Throughout: “σ Böotis” / “σ Boötis” spelling is inconsistent; standardize.","section":null},{"comment":"Appendix C pathways are useful but would be clearer if the competing rates (HSO recycling vs. photolysis) were quantified for the same G/K cases shown in Figure 3.","section":null},{"comment":"Data availability: the Zenodo/GitHub links are welcome; please confirm that the exact wavelength grid and units used by Atmos are included so that the prescription is plug-and-play.","section":null}],"recommendation":"minor_revision","confidential_remarks":"The proxy justification is the only load-bearing soft spot; once the authors either strengthen it or clearly demote the language to a sensitivity study, the paper is a solid, useful contribution for the journal. No novelty or citation-pattern concerns."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"This is a useful, well-executed sensitivity paper, not a breakthrough. The new piece is a better-motivated HSO cross-section prescription (truncated HSO2 data from Lu et al. 2021, justified by vibrational frequencies and Cs symmetry) plus the first quantitative demonstration that switching from the default HO2 proxy can raise tropospheric S8 by up to four orders of magnitude and strengthen haze features in transmission, emission, and reflection for G- and K-type hosts under elevated SO2 fluxes. They ship the data publicly. That is concrete and usable.\n\nWhat they do well: the comparison is cleanly isolated, boundary conditions are tabulated, Atmos + POSEIDON runs are standard and reproducible, and they correctly map where the effect appears (G/K, high SO2, cool troposphere) and where it vanishes (F and M). The spectral figures make the observational stakes for HWO/LIFE clear. Citation pattern is normal; no circularity.\n\nSoft spots are real but already flagged by the authors and the reader. The load-bearing assumption is that truncated HSO2 UV-Vis cross sections with QY=1 only for the HS+O channel are faithful enough that the S8 jumps are physically meaningful rather than proxy artefacts. They deliberately omit the second photolysis channel and any long-wavelength opacity tail. Free parameters (SO2 flux, surface T/RH) are chosen to maximize sensitivity. None of this is hidden, and the paper correctly frames itself as a prioritization exercise rather than a definitive HSO spectrum. Temperature dependence is also missing, which matters for hotter worlds.\n\nWho it is for: anyone running Archean-like sulphur photochemistry or planning haze-sensitive observations of G/K terrestrials. It does not rewrite the field, but it re-ranks a neglected radical and supplies a better default than HO2. Math and data look solid inside the stated model world. I would send it to peer review; the proxy caveat belongs in the discussion, not as a desk-reject reason. Worth citing when you next touch sulphur haze or UV cross-section priorities.","headline":"Clean sensitivity study that re-ranks HSO and shows large S8/spectral changes for G/K hosts; the result is real inside the model but rests on an unvalidated HSO2 proxy.","tokens_in":20027,"tokens_out":533,"would_cite":true,"duration_ms":5307,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"A better proxy for HSO photolysis boosts S8 haze signals in spectra of G- and K-star terrestrial planets with Archean-like air.","keywords":["Planetary Atmospheres","Exoplanet Atmospheres","Molecular Data","Radiative Transfer","HSO photolysis","S8 aerosols","Archean-like atmospheres"],"falsifier":"Laboratory or high-accuracy ab initio UV-Visible cross sections of HSO itself (including branching between HS+O and SO+H) that, when inserted into the same photochemical model under the same SO2 fluxes, erase or reverse the order-of-magnitude S8 enhancement relative to HO2.","tokens_in":20081,"feed_emoji":"☄️","tokens_out":952,"duration_ms":8396,"temperature":0.7,"pith_summary":"Photochemical models of temperate rocky exoplanets need accurate UV-Visible cross sections, yet HSO has none and is routinely treated as if it photolysed like HO2. This paper argues that HSO2 is a structurally better proxy, truncates its simulated spectrum at the energy needed to break the SO-H bond, and feeds the new prescription into an Archean-like N2-CO2-H2O atmosphere under elevated volcanic SO2. The result is higher HSO photolysis rates that feed sulphur polymerisation, producing tropospheric S8 abundances up to four orders of magnitude larger for G- and K-type hosts. Those aerosols strengthen optical scattering slopes and the 12 and 21 micrometre absorption features in transmission, emission and reflection spectra. Because S8 is a proposed indirect tracer of volcanic outgassing and a surface UV shield, the choice of HSO data can change whether those signatures appear strong enough to detect.","feed_headline":"Better HSO data boosts S8 haze signals around G and K stars","feed_subtitle":"A new HSO2-based proxy raises sulphur aerosol abundances by up to 10,000x in Archean-like air","key_machinery":"The updated HSO cross-section prescription: UV-Visible absorption of HSO2 truncated at 466.1 nm (quantum limit of the SO-H channel) with a constant quantum yield of 1 assigned only to the HS+O photolysis path, used inside a one-dimensional photochemical network to drive sulphur polymerisation to S8.","core_discovery":"Replacing the default HO2-based HSO cross sections with a truncated HSO2 spectrum raises integrated HSO photolysis rates and can increase tropospheric S8 abundances by up to four orders of magnitude for planets orbiting G- and K-type stars under elevated SO2 fluxes, thereby enhancing aerosol scattering and absorption signatures across transmission, emission and reflection spectra; F- and M-type hosts remain largely insensitive.","pith_inferences":["If the proxy is even approximately correct, HSO should be prioritised for laboratory or theoretical UV-Visible characterisation ahead of many other unmeasured radicals that do not feed S8 production.","Temperature-dependent HSO cross sections would be especially consequential for hot super-Earths with high sulphur outgassing, a regime the present cool-troposphere runs leave unexplored.","The same proxy logic (functional groups plus point-group symmetry) could be applied systematically to other unconstrained sulphur intermediates before full experimental campaigns."],"forward_implications":["S8 haze features at ~12 and ~21 micrometres may become detectable in emission for G-star planets under the new prescription, affecting LIFE-style planning.","Optical scattering slopes and geometric albedos rise for both G- and K-star cases, altering reflected-light observables relevant to future UV-optical-IR facilities.","S8 surface deposition rates can change by an order of magnitude, with direct consequences for modelled sulphur mass-independent fractionation records.","M-dwarf rocky planets remain robust to the choice of HSO data, so JWST interpretations of those atmospheres are not sensitive to this uncertainty."],"fun_headline_variants":["Updated HSO cross sections raise S8 by 10,000x around G-K stars","HSO2-based HSO rates amplify sulphur aerosol signals for G/K hosts","New HSO photolysis data boosts tropospheric S8 in Archean-like air","HSO cross-section swap heightens S8 haze signatures on G and K worlds","Better HSO UV data strengthens aerosol features for G/K exoplanets"],"cache_read_input_tokens":16512,"weakest_assumption_plain":"That HSO2 absorption, cut off at the SO-H bond energy and forced to yield only HS+O, is close enough to real HSO photolysis for the large S8 differences to be physically meaningful.","fun_headline_variants_meta":{"raw":{"variants":["Updated HSO cross sections raise S8 by 10,000x around G-K stars","HSO2-based HSO rates amplify sulphur aerosol signals for G/K hosts","New HSO photolysis data boosts tropospheric S8 in Archean-like air","HSO cross-section swap heightens S8 haze signatures on G and K worlds","Better HSO UV data strengthens aerosol features for G/K exoplanets"]},"model":"grok-4.5","effort":"low","cost_usd":0.003614,"raw_usage":{"total_tokens":1243,"prompt_tokens":865,"num_sources_used":0,"completion_tokens":114,"cost_in_usd_ticks":36140000,"prompt_tokens_details":{"text_tokens":865,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":264,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":865,"tokens_out":114,"duration_ms":3354,"temperature":1.0,"reasoning_tokens":264,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-11T20:26:40.497608+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"Laboratory or high-accuracy ab initio UV-Visible cross sections of HSO itself (including branching between HS+O and SO+H) that, when inserted into the same photochemical model under the same SO2 fluxes, erase or reverse the order-of-magnitude S8 enhancement relative to HO2.","supporting_citations":[],"review_version":1}