While focus in astrochemistry has traditionally been on diffusion driven reactions, we now place emphasis on radical driven, non-diffusive chemistry. Here, as illustrated in the figure below, an incoming radical, e.g., a hydrogen or oxygen atom, reacts with a molecule on the surface either by abstraction or addition, turning the molecule itself into a radical that may react with neighbouring molecules to
form increasingly complex molecular structures. Such reactions are sometimes referred to as “dark chemistry” and have been shown to drive the formation of glycine. We will determine whether H atom abstraction reactions, involving glycine embedded in realistic interstellar ice mixtures, provide a general pathway to the formation of all of the amino-acids relevant for life (Target-2). This proposed low temperature, low pressure formation pathway is dramatically different from amino acid formation in terrestrial chemistry. We will explore whether interstellar ice composition, molecular mixing and steric constraints related to the packing/layering of molecules in realistic interstellar ices may lead to selectivity in interstellar amino acid formation. We will investigate the structural and chiral properties of sugars formed via this pathway building on InterCat1 expected results (Target-4), and study radical driven bottom-up and top-down formation of nucleobases (Target-5). In addition, for the fatty acids (Target-3) we will build on the erosion reaction formation pathways previously identified and investigate the effect of hydrogen saturation, chain length and odd even characteristics on fatty acid formation and destruction.

WP2.1: Reaction pathways to amino acids beyond glycine and sugars

WP2.2: Carbon chemistry - pathways to fatty acid and nucleobase formation

WP2.3: Tracing ice evolution through isotopologues