Geochemical evolution of Gliese 1132 b influenced by internal mantle redox states

Star system: Gliese 1132 | Distance from the Sun: 41.1 light years

The internal state and atmospheric composition of rocky planets are heavily dictated by the exchange of gases between a molten mantle and the air above it. For planets orbiting very close to their stars, this process can continue for billions of years. A new analysis of the super-Earth Gliese 1132 b examines how the oxidation state of a planet's interior—specifically how oxygen availability affects the melting point of rocks—changes how these worlds cool and what gases they release into their atmosphere.

By using a computational model called PROTEUS, the research team simulated different internal environments. They found that in worlds with fewer volatile gases, the chemical "redox" state significantly alters when the mantle solidifies. A chemically reduced interior leads to an atmosphere rich in hydrogen and carbon monoxide, whereas an oxidized interior favors a thinner envelope of water vapor and carbon dioxide.

In systems with a large abundance of volatiles, the planet tends to maintain a global magma ocean regardless of these internal chemical variations. Ultimately, the total amount of volatile materials and the specific oxidation state serve as the primary controls on the planet's heat, providing specific patterns that may be identified in future light spectra observed by the James Webb Space Telescope.

Key findings
- Gliese 1132 b exhibits non-linear thermal responses based on its internal mantle melting properties.
- Reduced chemical environments within the planet favor massive hydrogen and carbon monoxide atmospheres.
- Oxidized chemical environments favor thinner atmospheres composed of water and carbon dioxide.
- Volatile-rich systems sustain steady-state global magma oceans regardless of mantle oxidation states.
- The total volatile inventory and surface oxygen levels are the primary regulators of planetary heat.

Scientific study

Geophysical and atmospheric implications of fO_{2}-dependent melting on rocky exoplanets (external link)