© 2021. The American Astronomical Society. All rights reserved.Rodríguez Almeida, L. F.Jimenez-Serra, IzaskunRivilla, Victor M.Martín Pintado, J.Zeng, ShaoshanTercero, B.De Vicente, P.Colzi, LauraRico Villas, F.Martín, S.Requena Torres, Miguel AngelUnidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-07372022-02-152022-02-152021-04-30The Astrophysical Journal Letters 912(1): L11(2021)2041-8205https://iopscience.iop.org/article/10.3847/2041-8213/abf7cbhttp://hdl.handle.net/20.500.12666/557The chemical compounds carrying the thiol group (-SH) have been considered essential in recent prebiotic studies regarding the polymerization of amino acids. We have searched for this kind of compound toward the Galactic Center quiescent cloud G+0.693–0.027. We report the first detection in the interstellar space of the trans-isomer of monothioformic acid (t-HC(O)SH) with an abundance of ~1 × 10−10. Additionally, we provide a solid confirmation of the gauche isomer of ethyl mercaptan (g-C2H5SH) with an abundance of ~3 × 10−10, and we also detect methyl mercaptan (CH3SH) with an abundance of ~5 × 10−9. Abundance ratios were calculated for the three SH-bearing species and their OH analogs, revealing similar trends between alcohols and thiols with increasing complexity. Possible chemical routes for the interstellar synthesis of t-HC(O)SH, CH3SH, and C2H5SH are discussed, as well as the relevance of these compounds in the synthesis of prebiotic proteins in the primitive Earth.engAttribution 4.0 Internationalhttps://creativecommons.org/licenses/by/4.0/AstrochemistryChemical AbundancesInterstellar moleculesGalactic centerinfo:eu-repo/semantics/article10.3847/2041-8213/abf7cb2041-8213http://dx.doi.org/10.13039/100012818http://dx.doi.org/10.13039/501100011033http://dx.doi.org/10.13039/501100000781http://dx.doi.org/10.13039/501100000780info:eu-repo/semantics/openAccess