Adsorption of glycine by cometary dust: Astrobiological implications

Glycine, the simplest amino acid, has been detected in the carbonaceous chondrites of several meteorites, and as well as in the comet Wild 2 embedded in the aerogel panel returned by the Stardust mission. A possible end state for glycine in comets is for it to form a molecule bond with another species of cometary dust. This paper aims to study the chemical interaction of a glycine molecule in its neutral and protonated form with the (100) surface of forsterite, a well-known cometary dust component, through electronic structure calculations based on the Density Functional Theory (DFT). Two models are investigated for the surface: dipolar and non-dipolar. The interaction of forsterite–glycine occurs via the two adsorption processes: physisorption and chemisorption, which depend on the configuration of the amino acid with the surface. When the amino acid reacts chemically with the surface (chemisorption process) the energies range from 58 to 96 kcal/mol. The calculated frequencies and normal modes of vibration of the most chemisorbed structures are in agreement with previous work in other surfaces.