Differential analysis of the spectra. The left panel shows the comparison between HERMES spectra of Europa, Vesta, and Victoria. The cyan histogram represents the distribution over the full spectral range, while the red histogram was calculated with the strongest telluric contribution excluded. The blue histogram indicates the distribution of the differences between the spectra of Vesta and Europa. The centre panel compares the two spectra from HERMES observations to the degraded Kurucz spectrum. In the right panel, the HERMES spectra are compared to the HARPS spectrum. In the centre and right panels, the blue, red, and cyan distributions depict the comparison of the reference spectra with the observations from Europa, Vesta, and Victoria, respectively. The same cleaning for telluric lines has been applied. The thin solid vertical and horizontal lines mark the theoretical centre of the distribution, while the dashed lines mark the borders of the 1σ (68.27%) interval. Accumulated and normalised histograms are shown on the right axis. The thick grey line depicts the shape of the accumulated theoretical Gaussian distribution.