On the Synthesis of Chocolate Flavonoids (Propanols, Butanals) in the Interstellar Medium

Complex organic molecules are ubiquitous in star- and planet-forming regions as well as on comets such as on 67P/Churyumov-Gerasimenko, but their origins have remained largely unexplained until now. Here, we report the first laboratory detection of distinct C₃ H₈ O (propanol, methyl ethyl ether) and C₄ H₈ O (n-butanal, i-butanal) isomers formed within interstellar analog ices through interaction with ionizing radiation. This study reveals that complex organics with propyl (C₃ H₇ ) and butyl (C₄ H₉ ) groups can be synthesized easily in deep space and may act as key evolutionary tracers of a cosmic ray driven non-equilibrium chemistry in low temperature interstellar ices at 10 K. These processes are of vital importance in initiating a chain of chemical reactions leading to complex organics-some of which are responsible for the flavors of chocolate-not only in the interstellar medium, but also on comet 67P/Churyumov-Gerasimenko.