Non-Equilibrium Growth Processes to Glyceraldehyde and Glycerol as Building Blocks of Interstellar Sugars and...

Complex organic molecules (COMs) such as aldoses and polyols are essential prebiotic compounds and serve as fundamental molecular building blocks for key biomolecules, including sugars and lipids. Despite their detection in star-forming regions and carbonaceous meteorites, the mechanisms of formation of these COMs in extraterrestrial environments remain largely controversial. Here, we demonstrate the bottom-up synthesis of a diverse set of COMs in the formaldehyde-water (H₂CO-H₂O) ice analogs subjected to simulated galactic cosmic rays (GCRs), including aldoses and polyols (glycolaldehyde, ethylene glycol, glyceraldehyde, and glycerol), as well as other compounds like glyoxal, methoxymethanol, (methoxymethoxy)methanol, formic acid, and methanetriol. The identification of these oxygen-bearing COMs was achieved using synchrotron vacuum ultraviolet photoionization reflectron time-of-flight mass spectrometry (SVUV-PI-ReToF-MS) during the temperature-programmed desorption (TPD) phase. Their unambiguous assignment was further confirmed by isotopic labeling experiments and by fitting the photoionization efficiency (PIE) curves of the parent product and fragment ions. The efficient synthesis of these COMs reveals constraints of the molecular complexity and reaction pathways available for forming aldoses and polyols in space, expanding our understanding of how such biorelevant precursors form in the extraterrestrial environments and their potential role in the abiotic origin of life on Earth.