γ-Ray-Driven Prebiotic Synthesis of DNA Backbone Sugars in Small Bodies

Abstract

Sugars play essential roles in genetic and metabolic processes. However, it remains unclear how the sugar backbone of DNA could have formed under prebiotic conditions. In the context of the RNA world hypothesis, the abiotic formation of ribose─the backbone of RNA─has been demonstrated by hydrothermal and γ-irradiation experiments under conditions simulating meteorite parent bodies. However, the abiotic synthesis of 2-deoxyribose─the backbone of DNA─from simple carbon sources, such as HCHO and CH3OH, has been limited. Here, we show that γ-irradiation under alkaline aqueous conditions simulating the interiors of meteorite parent bodies enables the formation of sugars, including both 2-deoxyribose and ribose, from simple carbon sources. These findings imply that ribose and 2-deoxyribose could have coexisted in small bodies from which carbonaceous meteorites originated, and been delivered to the early Earth, where they could have acted as precursors for RNA and DNA. More broadly, our results highlight the importance of radiation-driven chemistry within asteroids as a key contributor to a chemically diverse stage of early molecular evolution. Moreover, early chemical evolution may have involved a broader repertoire of sugar backbones than previously assumed and multiple noncanonical nucleic acids could have contributed to the origin of life.