{"id":"f5bd2fe3-3d09-48d4-84e5-93ca4885e47b","arxiv_id":"2504.12030","paper_version":2,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":7,"one_line_summary":"Even a perfectly reflective cloud deck cannot make a planet bright if the atmosphere above the clouds absorbs starlight, and K2-18b's spectrum caps its albedo near 0.2, below the ~0.6 needed for an ocean surface.","lead":"The paper shows that a planet's reflective power is capped by the thin atmospheric layer above its clouds, so an exoplanet's spectrum can rule out shiny-cloud habitability. Applied to K2-18b, the authors find its atmosphere reflects only about 17-18% of starlight, too little to keep a liquid water ocean, suggesting it is a magma-ocean or gas-dwarf world.","discovery_kind":"new_method","skeptic_critique":null,"referee_report":null,"author_rebuttal":null,"desk_editor":null,"rs_alignment":null,"lean_confirmation":null,"pith_extraction":null,"created_at":"2026-08-16T12:40:40.289005+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":null,"supporting_citations":[],"review_version":1}