Carbon dioxide (CO2) rich chlorine-bearing ices were exposed to energetic electrons in laboratory simulation experiments to investigate the formation of chlorine oxides (ClxOy) in the condensed phase on Mars. The radiolysis-induced synthesis of chlorine oxides (Cl xOy) was complementarily monitored online and in situ via infrared spectroscopy (IR) and quadrupole mass spectrometry (QMS). Three discrete chlorine oxides were identified: chorine dioxide (OClO), dichlorine monoxide (ClOCl), and chloryl chloride (ClClO2). Higher irradiation doses support the facile production of ClO3- and ClO 2-bearing high-order chlorine oxides. We attribute manifolds of chlorine oxides, as invoked herein, to the potential origin of perchlorates as found on Mars. © 2013 American Chemical Society.