{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"b18ccda346e233349efac4e60f1863895260e015fb893af05d549fcce9f4e518","created":"2026-10-03T07:17:55Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011","c1da01cccdab995103bb69427c0d76cbe17fda1b6a2e1c2046fa8d24c99ef764"],"salt":"87b9b8a370c24e765e63576f62e6d4fd22307de74031af9f4fa47b1850be9f45","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"astro.radius-valley.water-worlds","kind":"well-posed","literature_status":"open","n":"1","parents":[{"note":"","parent_revision":"c1da01cccdab995103bb69427c0d76cbe17fda1b6a2e1c2046fa8d24c99ef764","relation":"special_case"}],"plain":"Planets that formed beyond the line where water freezes and then moved inward could be up to half water by mass. Whether any such water worlds exist among close-in sub-Neptunes has not been shown.","posed_since":"","precise":"Determine whether any planet with $R \\sim 1.5-3.5\\ R_{\\mathrm{earth}}$ and $P < 100\\ \\mathrm{d}$ has a water mass fraction above 0.1, demonstrated by a combination of bulk density and an atmospheric mean molecular weight and H2O abundance that a rocky core with an H/He envelope or a magma-ocean model cannot reproduce. The answer is yes or no, with the planets and water fractions if yes.","problem_ref":null,"references":"","settled_by":"JWST spectra giving high mean molecular weight and H2O-dominated composition for a planet whose mass and radius are measured to better than 10 and 3 percent, fitted with interior models that include supercritical water and hydrogen-water mixing.","status_note":"A 2025 JWST analysis interpreted K2-18 b as water-rich (arXiv:2507.12622), but gas-rich mini-Neptune and magma-ocean models also fit its spectrum.","title":"Do sub-Neptunes with more than 10 percent water exist?","topic_ref":"29eecacca9d688759063e837d47b7481ed1a91ff74dcb512159e65510cf6039a"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"01c5f5dd665eae067eb5d6c8253423757d9d7fa5a4a0d2316a19ea2138c682b3","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"6e8f2f19b517efcd5e47403e93ec2d2449129ab265244683390ab163833c4d8c","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"Fa7afYj26N5nCvtfrlGx3LvXYHcW2bdQg9maAG6jy7zWSZ98hd14-djWX9zMpODRSCltTXcRDzvTW-lGB8gtAQ"},"schema":"pubphys.envelope/1"},"record_hash":"01c5f5dd665eae067eb5d6c8253423757d9d7fa5a4a0d2316a19ea2138c682b3","leaf_index":601}