Thiols in the Interstellar Medium: First Detection of HC(O)SH and Confirmation of C2H5SH

The 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 similar to 1 x 10(-10). Additionally, we provide a solid confirmation of the gauche isomer of ethyl mercaptan (g-C2H5SH) with an abundance of similar to 3 x 10(-10), and we also detect methyl mercaptan (CH3SH) with an abundance of similar to 5 x 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.

Automated summary

Compounds with thiol groups are crucial in the polymerization of amino acids in prebiotic studies. We have detected various thiol compounds in interstellar space, with different abundances. The ratios of thiol-bearing species to their alcohol analogs show similar trends in increasing complexity.