Understanding Atmospheres of Sub-Neptunes and Super-Earths Through Silicate-Hydrogen Interactions

Recent research published on arXiv investigates the phase equilibria of sub-Neptunes and super-Earths, focusing on the interactions between silicate materials and hydrogen-rich atmospheres. The paper, titled "Phase equilibria of sub-Neptunes and super-Earths," authored by Edward D. Young, Lars Stixrude, James G. Rogers, Hilke E. Schlichting, and Sarah P. Marcum, explores how these interactions influence planetary atmospheres and internal structures.

The study reveals that the silicate-hydrogen binary solvus plays a critical role in determining the characteristics of atmospheres on rocky planets that have acquired hydrogen-rich primary atmospheres. The researchers found that the temperature and pressure conditions for complete miscibility of silicate and hydrogen dictate the nature of these atmospheres. Specifically, the temperatures at the surfaces of supercritical magma oceans are linked to the silicate-hydrogen solvus, which suggests that the radial positions of magma ocean-atmosphere interfaces reflect the thermal states of these planets.

Additionally, the findings indicate that the solvus conditions significantly affect atmospheric structure, which in turn influences the transit radii of sub-Neptunes. The research also highlights that the separation of iron-rich metal to form cores in these planets is not guaranteed, due to the potential for neutral buoyancy of metal in silicate melt caused by the dissolution of hydrogen, silicon, and oxygen at high temperatures.

This research could have implications for understanding the formation and evolution of exoplanets, particularly those that fall into the categories of sub-Neptunes and super-Earths. The findings may help refine models of planetary atmospheres and contribute to the broader field of planetary science.

For further details, the paper can be accessed at arXiv:2408.11321.