Volume mixing ratio profiles of DMS, DMDS, hydrocarbons C₂H₆+C₂H₄+C₃H₄, and H₂S, in the atmosphere of K2-18b. Observational data points from N. Madhusudhan et al. (2025) and R. Hu et al. (2025) are shown alongside, initially attributed to DMS and/or DMDS but later shown to be consistent with alternative hydrocarbon species (e.g., R. Luque et al. 2025). DMS and DMDS production is sensitive to the input H₂S abundance (left) and the energy barrier to reaction (24) in pathway B (right), while the hydrocarbon production is not.