On the Quest for Glycine, Aminoacetic Acid, in the ISM

Aminoacetic acid, better known as glycine, has been sought for in the interstellar medium for a long time. Very recently, there has been a report on the detection of glycine in Sgr B2(N-LMH), Orion KL, and W51 e1/e2:
Y.-J. Kuan, S. B. Charnley, H.-C. Huang, W.-L. Tseng, and Z. Kisiel,
Interstellar Glycine
Astrophys. J. 593, 848–867 (2003).

This paper has caused quite a stir in the astronomical community, in particular if one considers the following paper:
J. M. Hollis, J. A. Pedelty, L. E. Snyder, P. R. Jewell, F. J. Lovas, P. Palmer, and S.-Y. Liu,
A Sensitive Very Large Array Search for Small-Scale Glycine Emission toward OMC-1
Astrophys. J. 588, 353–359 (2003).

It should be noted that the number of supposedly positively identified transitions reported by Kuan et al. is fairly large. Therefore, the report may be considered quite convincing.
However, it was brought to our attention that there seem to be some inconsistencies in the intensities of the lines. In particular, some of the observed lines seem to be too weak by a substantial amount that seems to be incompatible with the derived abundances and rotational temperatures. This may cast doubt on the derived abundances and possibly even on the interstellar detection.
At the moment it appears as if the publication of these reported inconsistencies will not settle the dispute of the glycine detection.

The paper alluded to in the previous paragraph is:
L. E. Snyder, F. J. Lovas, J. M. Hollis, D. N. Friedel, P. R. Jewell, A. Remijan, V. V. Ilyushin, E. A. Alekseev, and S. F. Dyubko,
A Rigorous Attempt to Verify Interstellar Glycine
Astrophys. J. 619, 914–930 (2005).

Overall, we would recommend the detection of glycine to be taken very cautiously.

Contributor(s): H. S. P. Müller; 12, 2004