Ion Irradiation of Frozen Methanol, Methane, and Benzene: Linking to the Colors of Centaurs and Trans‐Neptunian Objects

International audience; We present visible and near-infrared (0.65-2.7 mum) diffuse reflectance spectra of frozen (16-80 K) methanol (CH3OH), methane (CH4), and benzene (C6H6), collected before and after irradiation with 200 keV H+ and Ar+ ions, and 400 keV Ar++ ions, up to a dose released to target molecule of about 350 eV per 16 amu. The results evidence a strong reddening and darkening of the spectra, due to the formation of an organic (C-rich) refractory residue. The spectral behavior is compared with some Centaurs and trans-Neptunian objects; we find that many icy objects in the outer solar system may have grown an irradiation mantle, produced by cosmic ion irradiation of simple hydrocarbons and/or alcohols.