2025ApJ...995...67B

Planetary nebulae are sites where ejected stellar material evolves into complex molecules, but the precise physical conditions and chemical routes that govern these processes are unclear. The presence of abundant carbon-rich molecules in O-rich environments poses particular challenges. Here we report the first detection of methyl cation (CH${}_{3}^{+}$) in any planetary nebula, observed in the O-rich nebula NGC 6302 using JWST MIRI/Medium Resolution Spectrometer observations. CH${}_{3}^{+}$ is a key driver of organic chemistry in UV-irradiated environments. Spatially resolved observations reveal that CH${}_{3}^{+}$ is colocated with ¹²CO, H₂, H II, HCO⁺, and polycyclic aromatic hydrocarbons. LTE modeling of the CH${}_{3}^{+}$ emission yields excitation temperatures of 500-800 K in the inner bubble and torus, rising to 1000-2000 K in the outer bubble of NGC 6302, with column densities ranging from ∼10¹¹ to 10¹³ cm^–2. This detection suggests that hydrocarbon radical chemistry must be incorporated into planetary nebulae chemical models. Further near-IR observations are crucial to map different chemical networks operating in these environments.