Effect of Amorphous Ammonia-Water Ice onto Adsorption of Glycine on Cometary Dust Grain and IR Spectroscopy

The extraterrestrial origin of glycine has become a topic of great interest for astrobiology and it has been detected bonded to mineral surfaces in the dust of comet 81P/Wild 2 by the Stardust mission. The interactions of organic molecules with the dust grain surfaces shed light on possible routes for life from extraterrestrial space to Earth. The NH3 is one of the volatile components of cometary and interstellar ices. In this work we propose models that describe this scenario that consist of a quaternary system of one glycine molecule, a mixture of amorphous ammoniawater ice, and forsterite (100) surfaces (dipolar and nondipolar). Our quantum mechanical calculations show that the presence of amorphous ammonia/water ice increases the adsorption energy of glycine on the forsterite surface with respect to only amorphous water ice. In addition, we calculated the infrared (IR) frequencies to characterize the most reactive sites in the chemisorption processes with the mineral surface.