Much of the chemistry in circumstellar and interstellar regions is thought to be driven by gas–grain chemistry and, except for CO, most interstellar ices are formed in the solid phase. The most abundant solid species observed in space is by far water ice, icy mantles covering dust grains are ubiquitous, therefore water is almost always involved in the processes leading to prebiotic molecules. The physical properties of water ice mantles as a substrate have long been studied, they concern binding and diffusion energies of adsorbed molecules and atoms, ice morphology, trapping properties and thermal desorption.<br/>Recent developments in experimental and theoretical studies have triggered new insight into the physical-chemical properties of reactive systems including water molecules. Such studies reveal that non-thermal desorption is damped on water, hence crucial chemical routes like H additions, thought to be one-way only in the past, turn out to proceed in both directions. Also, experiments corroborated by quantum chemical calculations show that H abstraction may be inhibited by hydrogen bonding between reactants and the water ice structure. Throughout this talk I will show examples of how water-dominated icy mantles are able to change the balance between different branching ratios, by slowing down complete hydrogenation and by lengthening the interaction time between complex radicals.

Catalytic role of water ice in the formation of prebiotic molecules

2019 Fall National Meeting

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