2023ApJ...944..219N

Methyl mercaptan (CH₃SH) is one of the S-bearing organic compounds found in the interstellar medium (ISM). In this study, we investigated the surface reactions of solid CH₃SH with H atoms on amorphous solid water using experimental and computational methods to examine their physicochemical behavior in the ISM. Consequently, the primary product was discovered to be CH₄. As the computational studies show that the dominant reaction pathway is H + CH₃SH → CH₃ + H₂S, the observed CH₄ would result from H addition to CH₃. As relatively minor routes, the H abstraction processes from the -CH₃ and -SH functional groups of CH₃SH, giving rise to CH₂SH and CH₃S radicals, are confirmed. Although these radicals may form CH₃SH again by reactions with H atoms, the loss of CH₃SH from the ice surface by chemical desorption would be minor.