Mechanochemical Reactivity of Ribonucleosides Mediated by Inorganic Species: Implications for Extraterrestrial Organic Matter Interpretation

Metal species and carbonate are often found as minerals in extraterrestrial rocky bodies. Based on this, the mechanochemical-induced degradation of canonical purine and pyrimidine ribonucleosides into their corresponding nucleobases mediated by some of the main constituents of those materials (iron, nickel, or aluminum) was accomplished. In some cases, the previous heating of the samples intensified mechanochemical degradation. Additionally, carbonate acts as an activator for ribonucleoside degradation with a catalyst (a Lewis acid ion); however, it has almost no effect on ribonucleoside degradation in the absence of a catalyst. These results can contribute to the hypothesis that organic matter in extraterrestrial samples could have undergone mechanochemical reactions (i.e., shock/impact events), from its formation until its journey to Earth. Mechanochemical energy could occur in planetesimal accretion, asteroid formation (i.e., through planetesimal disintegration), and meteoroid atmospheric entry. Additionally, this hypothesis can clarify and relate some identified biosignatures with pathways of prebiological evolution.