Scientists have been struggling to detect and study small, faint exoplanets like K2-18 b, a temperate sub-Neptune orbiting an M-dwarf star. However, recent observations using the Hubble Space Telescope (HST) and James Webb Space Telescope (JWST) reveal that K2-18 b’s atmosphere may be rich in hydrogen, methane, and possibly carbon dioxide.
Researchers used a new model to analyze the data and constrain atmospheric parameters such as metallicity, C/O ratio, and vertical mixing. The study found that K2-18 b’s atmosphere likely has high metallicity and a C/O ratio greater than 2.1, which could indicate aerosol formation. Methane is robustly detected in the atmosphere.
However, some uncertainties remain, particularly when it comes to carbon dioxide. Future observations with JWST’s NIRSpec instrument will be crucial for refining models and probing habitability.
This study highlights the importance of non-equilibrium chemistry in understanding exoplanet atmospheres. By analyzing data from K2-18 b, researchers can better constrain atmospheric parameters and gain insights into the potential for life on this distant world.
Source: https://astrobiology.com/2025/07/unraveling-the-non-equilibrium-chemistry-of-the-temperate-sub-neptune-k2-18-b.html