Researchers at the University of Hawaiʻi at Mānoa Department of Chemistry’s W.M. Keck Research Laboratory in Astrochemistry, along with colleagues at the universities of Virginia and Southern California, have provided conclusive evidence about complex organic molecules: formation of these key molecules, relevant to the origin of Earth’s living organisms such as aldehydes and ketones, is driven by a cosmic-ray-triggered nonequilibrium chemistry deep within interstellar ices at temperatures as low as 5 Kelvin (-450°F). The evidence was based on laboratory experiments, computations and modeling.
The newly published research paper, “A study of interstellar aldehydes and enols as tracers of a cosmic ray-driven nonequilibrium synthesis of complex organic molecules,” was authored by graduate student Matt Abplanalp and Professor Ralf Kaiser in the Proceedings of the National Academy of Sciences. This article has already gained recognition in the United Kingdom as well as from the journal Nature.
“On Earth, cosmic ray exposure is deadly to humans since the radiation can lead to the degradation of deoxyribonucleic acid (DNA), which is a molecule carrying the genetic instructions used in the growth, development, functioning and replication of all known living beings,“ said Abplanalp. “But in deep space, cosmic rays drive unique chemical reaction pathways to actually initiate the formation of biorelevant molecules, which eventually might jumpstart the molecular evolution of life as we know it.”
In an ultra-high vacuum chamber cooled down to 5 Kelvin, the Hawaiʻi team simulated icy grains coated with carbon monoxide and methane/ethane. When exposed to high-energy electrons, to mimic the cosmic rays in space, aldehydes and energetically unfavorable enols are synthesized in exotic nonequilibrium reactions. This work challenges a conventional wisdom that a higher temperature is necessary to recombine reactive radicals, whereas the present findings reveal explicitly that those organics can be formed at ultra-low temperatures.
These processes are crucial in starting the chain of chemical reactions that lead to the formation of biorelevant molecular precursors in space and will assist in the understanding of the origin as well as the evolution of the molecular universe.