Chemical Environment and Temperature Effects on the Formation and Destruction of C 3 O 2 in Cosmic-Ray-Processed Ices

High Resolution Image Download MS PowerPoint Slide Astrophysical ices composed of CO and CO 2 undergo complex radiation-driven chemistry, producing reactive species with potential prebiotic relevance. Using the PROCODA kinetic model (642 coupled reactions, 18 tracked species) combined with ion irradiation data, we investigate the main formation and destruction pathways of carbon suboxide (C 3 O 2 ) in CO-, CO 2 -, and mixed CO/CO 2 -rich ices. A clear two-regime picture emerges. At early fluence, chemistry is matrix-controlled: in pure CO ice, C 3 O 2 forms mainly via CO + C 2 O → C 3 O 2, whereas in pure CO 2 ice it proceeds via CO 2 + C 2 O 2 → O 2 + C 3 O 2; mixed ices retain CO-involving channels. At chemical equilibrium, routes shift as accumulated intermediates take over: in CO ice, C 3 + CO 2 → C + C 3 O 2 dominates, while in CO 2 ice, CO + C 2 O 2 → O + C 3 O 2 prevails. Destruction is likewise environment-sensitive: C 3 O 2 + R → CO + C 2 O leads in CO ice, versus C 3 O 2 + R → C + C 2 O 2 in CO 2 ice ( R denotes radiation-induced processes). Raising the temperature from 10 to 20 K enhances bimolecular channels through greater molecular mobility, while leaving radiation-driven pathways largely unaffected. Using C 3 O 2 as a prototype, this study provides pathway maps that link composition, temperature, and irradiation history, offering new constraints for astrochemical models and for interpreting JWST and ALMA observations.