Perchlorate (ClO4-) has been detected on Mars, but its production and distribution are unclear. Mechanisms requiring atmospheric chlorine are insufficient for measured concentrations. We conducted studies under Mars conditions using halite (NaCl) alone, soil simulants consisting of silica (SiO2), Fe2O3, Al2O3, and TiO2. After 170 h irradiation, samples analyzed by ion chromatography (IC) showed ClO4- and ClO3- present in all samples. When SiO2 was added, yield increased from 2 to 42 nmol and 0.4 to 2.6 nmol, respectively. We attribute this to SiO2 and metal oxides acting as photocatalysts, generating O2- radicals from O2 which react with chloride. Results show ClO4- and ClO3- can be produced photochemically on Cl minerals without atmospheric chlorine or aqueous conditions, and explain high concentration of ClO4- and ClO4-/Cl- ratios detected by Phoenix. They provide evidence that its distribution on Mars is dictated by distribution of chlorine and provide insight into the oxidizing nature of the soil and its potential effects on organics.