Hydrogen sulfide has been detected in seven star-forming regions very early as a very abundant molecule via its 1₁₀ – 1₀₁ transition in the 2 mm region:
P. Thaddeus, M. L. Kutner, A. A. Penzias, R. W. Wilson, and K. B. Jefferts,
Interstellar Hydrogen Sulfide
Astrophys. J. 176, L73–L76 (1972).
H₂S was also identified in this transition toward the circumstellar envelope of OH231.8+4.2:
N. Ukita, M. Morris,
Hydrogen Sulfide in a Circumstellar Envelope
Astron Astrophys. 121, 15–18 (1983);
and also in certain regions of the cold dark clouds L134N and TMC-1:
Y. C. Minh, W. M. Irvine, and L. M. Ziurys,
Detection of Interstellar Hydrogen Sulfide in Cold, Dark Clouds
Astrophys. J. 345, L63–L66 (1989).

The same transition was used to identify H₂³⁴S toward certain regions in the Orion molecular cloud:
Y. C. Minh, W. M. Irvine, D. McGonagle, and L. M. Ziurys,
Observations of the H₂S toward OMC-1
Astrophys. J. 360, 136–141 (1990).

A weak feature near 333 GHz has been identified as the 2₀₂ – 1₁₁ of HDS:
G. H. Macdonald, A. G. Gibb, R. J. Habing, and T. J. Millar,
A 330–360 GHz Spectral Survey of G 34.3+0.15. I. Data and Physical Analysis
Astron Astrophys. Suppl. Ser. 119, 333–367 (1996).

Even D₂S was recently detected toward two dense, cold clouds Barnard 1 and NGC 1333 IRAS 4A(DCO⁺), with HDS detected toward several additional sources:
C. Vastel, T. G. Phillips, C. Ceccarelli, and J. C. Pearson,
First Detection of Doubly Deuterated Hydrogen Sulfide
Astrophys. J. 593, L97–L100 (2003).

HD³⁴S was identified in
The ALMA-PILS Survey: The Sulfur Connection between Protostars and Comets: IRAS 16293–2422 B and 67P/Churyumov-Gerasimenko
Mon. Not. R. Astron. Soc. 476, 4949–4964 (2018) by
M. N. Drozdovskaya, E. F. van Dishoeck, J. K. Jørgensen, U. Calmonte, M. H. D. van der Wiel, A. Coutens, H. Calcutt, H. S. P. Müller, P. Bjerkeli, M. V. Persson, S. F. Wampfler, and K. Altwegg.
Only the 2₀₂ – 1₁₁ transition was detected clearly for HD³⁴S and HDS at 332255 and 333279 MHz, respectively. Other lines in the survey were too weak to be detected, as expected. An important detail is that the ratio of approximately 20 is close to the terrestrial value.

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Contributor(s): H. S. P. Müller; 10, 2008; 08, 2018

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