Reflation: Redox-Driven Atmospheric Inflation as Tracer of Super-Earth Geochemistry

Journal article

Abstract We demonstrate that the redox-sensitivity of mantle outgassing can trigger transient episodes of atmospheric reinflation in highly irradiated and geochemically reduced super-Earths, a mechanism we term “reflation.” Mantle redox governs the outgassing and speciation of CHONS volatiles, setting the background secondary atmospheric composition during extended photoevaporation at highly irradiated conditions. Using simulations of the coupled atmosphere–interior evolution of irradiated super-Earths, we illustrate that reduced mantles close to the iron–wüstite buffer initially produce CO-dominated atmospheres. Hydrodynamic escape continuously removes volatiles while outgassing from the melt replenishes the atmosphere with H 2 , converted from H 2 O dissolved in the underlying magma ocean. This leads to a late-stage transition from C- to H-dominated gas that transiently reinflates super-Earth atmospheres and decreases their bulk densities by up to ∼60% between several hundreds of megayears to a gigayear after their formation, prior to complete atmospheric erosion by photoevaporation. In contrast, oxidized mantles, closer to Earth-like geochemistry, strongly buffer their atmospheric composition while exposed to hydrodynamic escape, producing monotonic radius deflation. Reflation events are triggered by geochemically reduced mantles, intermediate escape efficiencies, high irradiation, and initial water inventories ≳ 5 Earth oceans. This redox-dependent evolutionary divergence hinges on the sensitive feedback between interior and atmospheric evolution serving as a potential tracer of historical geochemical state. Population-level reflation signatures of close-in super-Earths may thus serve as tracers of interior geochemistry and formation conditions.

Authors: Cesario, L; Lichtenberg, T; Attia, M; Nicholls, H; Kisvárdai, I

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Astronomical Society
• Journal: The Astrophysical Journal Letters
• Volume: 1007
• Issue: 1
• Pages: L8-L8
• Publication date: 2026-08-03
• DOI: 10.3847/2041-8213/ae8b95
• EISSN: 2041-8213
• ISSN: 2041-8205
• Language: English
• Keywords: TRACER; Atmosphere (unit); Basalt; Atmospheric escape; Atmospheric pressure; Atmospheric chemistry; Mantle (geology); Methane; Outgassing