Planetary nebula NGC 6302 - a testbed for dust formation and processing in a dense torus irradiated by harsh UV radiation

Dust is a key ingredient in galaxies, because it provides opacity, plays a key role in interstellar chemistry, and is essential for the formation of stars and (rocky) planets. Evolved Asymptotic Giant Branch (AGB) stars are an important source of stardust in galaxies. The processing of this dust in the interstellar medium (ISM) can be traced by comparing the composition of stardust to that of interstellar dust. For instance, the fraction of crystalline silicate dust in starburst galaxies is used to measure the input of fresh stardust by O-rich evolved stars in the ISM. It is unclear however in what form stardust from AGB stars enters the ISM. This is because: (1) evidence is accumulating that their winds have complex, non-spherical structures, such as disks/tori, often associated with (sub-)stellar companions; and (2) it is unclear how freshly made stardust is affected by the harsh environment that prevails in planetary nebulae (PNe), whose central stars have fast winds and extreme radiation fields. The PN NGC6302 offers a unique laboratory to study the physical and chemical processing of a dense dusty molecular torus ejected by an AGB star, which is exposed to the radiation field and stellar wind of the hottest star known in the Galaxy. Spatially unresolved observations by ISO have revealed a complex chemistry, showing emission from C-rich Polycyclic Aromatic Hydrocarbons (PAHs) in an O-rich chemistry, as well as a very profuse circumstellar dust mineralogy. Spatially resolved JWST observations will allow us to witness how the AGB ejecta are processed in the nebular environment, and to establish in what form the solids in its ejecta are delivered to the ISM.