Sulfur (S) 2p photoelectron spectra comparison. Normalized high-resolution S 2p photoelectron spectra of C0242 and A0226 particles. The grain A0226 shows a weak S 2p signal composed of at least two components: one attributable to a reduced sulfur species (S(1), likely S²⁻) and another at higher BE, consistent with more oxidized sulfur specie [S(2)]. Under the same experimental conditions, these spectral features were not detected on the C0242 particle.