URSO, Riccardo GiovanniRiccardo GiovanniURSOBaklouti, DoniaDoniaBakloutiDjouadi, ZahiaZahiaDjouadiPinilla-Alonso, NoemíNoemíPinilla-AlonsoBrunetto, RosarioRosarioBrunetto2022-11-212022-11-2120202041-8205http://hdl.handle.net/20.500.12386/32726Frozen methanol was detected in the outer solar system on the surfaces of the Centaur 5145 Pholus, the Trans-Neptunian Object (55638) 2002 VE<SUB>95</SUB>, and more recently on (486958) Arrokoth. The icy surfaces of these objects are subjected to solar and cosmic ions that modify the physico-chemical properties of their surface. To study the effects of ion bombardment on methanol-rich surfaces, we performed experiments of ion irradiation of H<SUB>2</SUB>O:CH<SUB>3</SUB>OH mixtures and we monitored the evolution of the methanol near-infrared bands. We observed significant variations of the 2.34/2.27 μm methanol band ratios as a function of the irradiation dose. We then used the Arrokoth and Pholus spectra to test the 2.34/2.27 μm band ratio as a probe of irradiation of methanol-rich surfaces, and we estimated the timescales of processing by solar and cosmic ions. Our results indicate that solar energetic particles are the main drivers of changes in the near-infrared spectra of frozen surfaces in the outer solar system.STAMPAitArticle10.3847/2041-8213/ab8ad92-s2.0-85086328583https://iopscience.iop.org/article/10.3847/2041-8213/ab8ad9https://api.elsevier.com/content/abstract/scopus_id/850863285832020ApJ...894L...3UFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation