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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 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