Methyl mercaptan (CH₃SH) was first identified in Sgr B2 in 1979 by Linke et al. via six rotational lines. It was detected toward the hot core G327.3-0.6 by Gibb et al.. Torsionally excited methyl mercaptan was observed in Sgr B2 by Müller et al. and reported in 2016. Methyl mercaptan was searched for but not detected in the dark clouds TMC-1 and L134N. While methyl mercaptan has not been observed to date on any of the other Solar System planets, it could be used as a biomaker for detecting evidence of Martian life.

Methyl mercaptan is a close cousin of methanol (CH₃OH), with the O atom replaced by S. While the odors of methanol and similar alcohols are distinctive, they are nothing in constrast to mercaptans, also known as thiols. Methyl mercaptan is used as an odorant in natural gas. As Wikipedia notes, methyl mercaptan