Interstellar glycine

We have searched for interstellar conformer I glycine (NH2CH2COOH), the simplest amino acid, in the hot molecular cores Sgr B2(N-LMH), Orion KL, and W51 e1/e2. An improved search strategy for intrinsically weak molecular lines, involving multisource observations, has been developed and implemented. In total, 82 spectral frequency bands, in the millimeter-wave region, were observed over a 4 yr period; 27 glycine lines were detected in 19 different spectral bands in one or more sources. The rotational temperatures derived from "rotation diagrams" are 75(-16)(+29) K for Sgr B2(N-LMH), 141(-37)(+76) K for Orion KL, and 121(-32)(+71) K for W51 e1/e2. The total column densities inferred are 4.16(-1.8)(+3.22) x 10(14) cm(-2) for Sgr B2, 4.37(-1.27)(+1.79) x 10(14) cm(-2) for Orion, and 2.09(-0.77)(+1.22) x 10(14) cm(-2) for W51. Production of interstellar glycine by both gas-phase ion-molecule reactions and by ultraviolet photolysis of molecular ices is briefly discussed. The discovery of interstellar glycine strengthens the thesis that interstellar organic molecules could have played a pivotal role in the prebiotic chemistry of the early Earth.