Oxygen chemistry in interstellar ices

Abstract

Astronomical observations conducted in both star-forming regions and cometary environments have revealed the presence of numerous organic species, both aromatic and oxygenic, suggesting the presence of a diverse organic (astro)chemistry active even at the extremely low temperatures (~10–50 K) characteristic of these environments.

Due to the low temperatures, many molecules condense in the ices that coat interstellar dust grains, facilitating chemical reactions.
Laboratory studies show that UV irradiation of complex ices favors the formation of new chemical species both through direct photo initiated processes and through energetic species generated by fragmentation that fuel further chemical reactions.

In this context, the role of atomic oxygen, particularly in its excited state O(1D), in the chemistry of astrophysical ices is being studied as a possible driver of molecular complexity.
Experiments conducted on ices formed under ultrahigh vacuum conditions and at cryogenic temperatures show that oxygen insertion represents an efficient channel for the oxidation and functionalization of a variety of organic molecules.

In this work, we study the insertion of O(1D) into acetaldehyde to form glycolaldehyde and acetic acid, and the parallel reaction of atomic oxygen in aromatic systems to form oxygenated derivatives. Both processes highlight how reactions induced under cryogenic conditions can contribute to the growth of chemical complexity, leading to species of prebiotic interest.

Overall, the results suggest that O(1D)-induced chemistry in ices represents a plausible pathway for the formation of complex organic molecules, including sugar precursors, in the early stages of star and planet formation.