In a recent study, a team of researchers from the University of Bern, Harvard University, and the University of Copenhagen have shed light on the chemical processes that could enrich icy planetesimals with complex organic molecules, potentially relevant to the origins of life. The team, led by Elettra L. Piacentino, conducted experiments to investigate the reactivity of atomic oxygen with benzene ices, a process that could occur in the cold, dense regions of interstellar clouds where stars and planets form.
The researchers focused on the reaction of singlet oxygen atoms, denoted as O(^1D), with benzene, a simple aromatic molecule. They used ozone as a precursor, which readily dissociates under low-energy ultraviolet light to produce O(^1D) atoms. The experiments revealed that O(^1D) efficiently reacts with benzene, forming phenol, benzene oxide, and oxepine as the main products. Phenol formation was found to be temperature-independent, suggesting a barrierless insertion mechanism. In contrast, the formation of benzene oxide and oxepine showed a slight temperature dependence, indicating that additional reaction pathways might be involved.
The researchers also examined the effect of dilution on the formation of these products in H2O and CO ice matrices. They found that dilution did not suppress the formation of phenol, which is a significant finding given the low densities and temperatures of interstellar clouds. Based on their experimental results, the team extrapolated an upper limit for the benzene-to-phenol conversion fraction of 27-44% during the lifetime of an interstellar cloud. This estimate is based on O(^1D) production rates derived from CO2 ice abundances and a cosmic-ray induced UV field.
To validate their findings, the researchers compared their estimates with data from the comet 67P, where oxygen-bearing aromatic molecules have been detected. They found that the C6H6O/C6H6 ratio in the comet’s coma was 20±6%, a value that lies within their estimated range. This agreement suggests that O(^1D)-mediated chemistry is a viable pathway for producing oxygenated aromatics in cold astrophysical ices.
The practical applications of this research for the energy sector are not immediately apparent, as the study focuses on fundamental chemical processes in astrophysical environments. However, understanding the formation and evolution of complex organic molecules in space can provide insights into the origins of life and the potential for life beyond Earth. This knowledge could inform the search for extraterrestrial life and the development of technologies for detecting and analyzing organic molecules in extreme environments, which could have implications for energy exploration and resource management in the future.
The research was published in the journal Nature Astronomy.
This article is based on research available at arXiv.