Water on Hot Rocky Exoplanets

Abstract Data suggest that most rocky exoplanets with orbital period p < 100 days (“hot” exoplanets) formed as gas-rich sub-Neptunes subsequently lost of their envelopes, but whether these still have atmospheres is unknown. We identify a pathway by which 1–1.7 R ⊕ (1–10 M ) periods 10–100 can acquire long-lived 10–2000 bar are H 2 O-dominated, mean molecular weight >10. These form during the planets’ evolution from into exoplanets. O made reduction iron oxides in silicate magma highly soluble magma, forming dissolved reservoir protected loss so long -dominated atmosphere persists. The large size buffers against after has dispersed. Within our model, long-lived, water-dominated common outcome for efficient interaction between nebula-derived (peak mass fraction 0.1–0.6 wt%) and oxidized (>5 wt% FeO), followed atmospheric loss. This idea predicts planets radii within 0.1–0.2 lower edge radius valley retain atmospheres. prediction imminently testable James Webb Space Telescope implications interpretation data transiting super-Earths.