Magma Oceans Influence Atmospheric Composition of Sub-Neptune Exoplanets

Recent research has highlighted the significant role of magma oceans in influencing the atmospheric composition of sub-Neptune exoplanets. The study, titled "Role of magma oceans in controlling carbon and oxygen of sub-Neptune atmospheres," authored by Chanoul Seo, Yuichi Ito, and Yuka Fujii, was submitted to arXiv on August 30, 2024.

The authors investigated how various planetary parameters—such as atmospheric thickness, planetary mass, equilibrium temperature, and magma properties—affect the levels of hydrogen (H), oxygen (O), and carbon (C) in the atmospheres of these planets. They utilized an atmosphere-magma chemical equilibrium model to analyze the interaction between accreted volatiles and molten rocky surfaces, known as magma oceans.

Key findings from the research indicate that the fraction of water vapor (H₂O) in the atmosphere of a fully molten rocky interior with an Earth-like redox state is consistently around 1% to 10%, regardless of other planetary characteristics. Additionally, the study revealed that the carbon-to-hydrogen ratio (C/H) increases only slightly above the nebula value under specific atmospheric pressures and water vapor fractions. This results in a negative trend between oxygen-to-hydrogen (O/H) and carbon-to-oxygen (C/O) ratios, suggesting that the atmospheric composition can provide evidence of a rocky interior and the presence of endogenous water.

The implications of these findings are significant for understanding the atmospheric evolution of sub-Neptune exoplanets. By characterizing the chemical interactions occurring in magma oceans, the study contributes to the broader knowledge of planetary formation and the potential habitability of these distant worlds. The research emphasizes the need for further constraints on high-pressure material properties to enhance interpretations of magma-atmospheric interactions in inflated planets.

For more details, the paper can be accessed at arXiv:2408.17056.