Principal component (PC) plot for olivine (OL) and pyroxene (OPX) subject to different irradiation set-ups and including S-, Q-, V-, and A-type asteroids. Each letter (spectral type) in the graph represents the position of one asteroid in the principal component space. The spectra of irradiated pellets have the same positions as in Fig. 8 (top); for better readability, only hydrogen (H⁺) and laser irradiation are shown. The most irradiated spectra are indicated by the arrows’ tips (the maturation thus goes from the lower left to the top right corner).