{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"39ec2e058e40e5ddabe1ae0ad7def32707c1bef9ea34325c59cc9eeae167354e","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["c1da01cccdab995103bb69427c0d76cbe17fda1b6a2e1c2046fa8d24c99ef764","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"b5c32996474248af3947e5d736360cb8c21e64c10b063b2ddc34c83042ec7f1b","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"classification","assisted_by":[],"external_id":"astro.radius-valley.sub-neptune-composition","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"A planet two or three times Earth's size can be a rocky ball with a thin hydrogen layer or a world with a large fraction of water, and mass and radius alone cannot tell which. Their atmospheres carry clues.","posed_since":"","precise":"For planets with $R \\sim 2-3.5\\,R_{\\mathrm{earth}}$ and $M \\sim 5-15\\,M_{\\mathrm{earth}}$, determine the bulk composition: rocky cores with H/He envelopes of $\\sim 1-3\\%$ by mass, water mass fractions of $\\sim 10-50\\%$ in supercritical layers, or magma oceans that dissolve and mix with hydrogen. The answer is a classification of individual planets and the population fractions, using JWST transmission spectra (mean molecular weight, $\\mathrm{H_2O}$, $\\mathrm{CH_4}$, $\\mathrm{CO_2}$, $\\mathrm{NH_3}$ abundances) together with interior models.","problem_ref":"c1da01cccdab995103bb69427c0d76cbe17fda1b6a2e1c2046fa8d24c99ef764","references":"","settled_by":"High signal-to-noise transmission and emission spectra of a sample of temperate and warm sub-Neptunes fitted with coupled interior-atmosphere models.","status_note":"","title":"Are sub-Neptunes rocky cores with hydrogen or water worlds?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"f19a6f4a8e5c414013b847bcfedba15ddd9d28ff58ba0aa3126e465c1a8b38af","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"b3f8b771adf64fdd55274133b084cf02f4059d5335653a474ef322d3745ef97f","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"eo5sgBNWT1YPAsZKMDvlwJeEEPE1wLZadQx52ItG6RvxBXzsiKWvc8q6NW6CvGULY-taO7gM8lqPZ30IOVhuAA"},"schema":"pubphys.envelope/1"},"record_hash":"f19a6f4a8e5c414013b847bcfedba15ddd9d28ff58ba0aa3126e465c1a8b38af","leaf_index":2416}