Hydrogen Atmospheres on Scorching Planets: The Volcano Secret ⚡ экспресс
Rocky exoplanets close to stars on eccentric orbits can retain a hydrogen atmosphere through volcanic degassing driven by tidal heating. A model of the interior and atmosphere was developed to assess the ability of volcanism to sustain an H₂-dominated environment over geological timescales (≥1 billion years). It accounts for redox state, tidal heat, volatile inventory, and orbital parameters, computing gas fluxes and comparing them with energy-limited hydrodynamic escape. It was found that a water-saturated magma ocean, reduced melts, and high eccentricity are necessary. A thin hydrogen envelope is a sign of ongoing magmatic activity. A 'degassing zone' (parameter space favorable for such planets) was defined, and promising targets were identified. Joint analysis of precise masses, radii, eccentricities, and JWST measurements of mean atmospheric molecular weight will enable the search for these worlds; and a robust non-detection of an atmosphere will provide constraints on melt redox state, melt fraction in the mantle, and heat flow.
Many planets around other stars — exoplanets — have elongated orbits. With each close approach, the star’s gravity squeezes and stretches them, like kneading dough. Friction heats up the interior to the point where rock melts, creating underground oceans of magma.
In this scorching mix, water from minerals breaks apart and releases hydrogen. The lightweight gas tries to escape, like steam from a pot, but non-stop volcanic eruptions belch out fresh supplies. The planet resembles a boiling soup: evaporation is offset by adding broth. This sustains a thin hydrogen envelope that would otherwise be whisked away into space.
James Webb detects such worlds when they pass in front of the star’s disk. The transmission spectroscopy method reveals absorption in a hydrogen haze — a sign of relentless volcanism. If there’s no envelope, then the interior has little water or the magma has cooled. Most remarkably, from the thickness of this layer, astronomers can gauge the eruption strength on a planet they’ll never see through a telescope.
🎯 On Jupiter’s moon Io, tidal heating powers hundreds of active volcanoes — the most powerful eruptions in the Solar System.