H₂CO in H₂O:CH₃OH:NH₃ mixtures exposed to ion bombardment. Estimates are based on the analysis of the 1250 cm⁻¹ band for H₂CO and 1025 cm⁻¹ for CH₃OH and are normalized to the initial methanol abundance, (CH₃OH)i. Panel A: H₂CO as a function of dose, with respect to the amount of deposited CH₃OH. The grey area shows the range in which the H₂CO abundance was found to increase with increasing the dose. The horizontal dashed line indicates the maximum amount of H₂CO found in 1:1:1 mixtures (dashed black line) and 3:1:1 mixtures (dashed grey line). Panel B: H₂CO with respect to the CH₃OH at the same irradiation dose.