New Insights into Sub-Neptunian Planets

A recent study led by ETH Zurich in collaboration with researchers from the Max Planck Institute for Astronomy in Heidelberg and the University of California, Los Angeles, has revealed new findings about planets known as “sub-Neptunian,” which do not exist in our solar system. These planets are common in outer space but differ from those we know in our system.

Concept of Hycean Planets

The prevailing hypothesis was that these planets could contain large amounts of water beneath a hydrogen-rich atmosphere. These planets were described as “Hycean,” a term combining “hydrogen” and “ocean.” This concept suggested the presence of vast oceans beneath the atmosphere of these planets.

However, the recent study questioned this hypothesis, showing that this scenario is impossible due to chemical interactions between the atmosphere and the planet’s interior that were previously overlooked.

Chemical Interactions and Their Impact

According to Dr. Dorn, previous studies failed to consider the chemical interactions between the atmosphere and the planet’s interior. Aron Weerlin, the lead researcher of the study, explained that these interactions could lead to the destruction of water molecules (H2O), as hydrogen and oxygen bond with metallic compounds, causing most of the water to disappear into the planet’s core.

The study uses a model to describe the evolution of planets over a certain period, incorporating a new model to calculate the chemical processes occurring between the atmospheric gas and the minerals and silicates in the molten ocean.

Concept of Sub-Neptunian Planets

Sub-Neptunian planets are larger than Earth but smaller than Neptune, forming a category of planets not found in our solar system. The study showed that these planets might have started as planets covered with oceans of hot lava, surrounded by a hydrogen gas atmosphere that maintained this state for several million years.

These findings are intriguing as they indicate that planets formed within the “snow line” have atmospheres rich in water, rather than those that accumulated large amounts of ice.

Conclusion

This study highlights the need to reassess our understanding of the formation of exoplanets, particularly concerning the formation of water and its role on these planets. The results emphasize the importance of chemical interactions between the molten ocean and the atmosphere in shaping the composition of planets, prompting a reevaluation of planetary formation theories and the interpretation of exoplanetary atmospheres. These discoveries complicate the search for life beyond Earth, suggesting that suitable conditions for life may exist only on smaller planets, which can only be observed using more advanced observatories than the James Webb Space Telescope.