Intimate Link Between Prebiotic Chemistry and Meteorites: Mechanisms of Organic Molecule Formation.

Abstract

Whether meteorites brought ingredients necessary for the origin of life exogenously or they were produced endogenously on early Earth, having a prebiotic chemical inventory of organic compounds associated with meteorites is critical, as it represents a window into the organic compound building blocks available for the emergence of life. Understanding the prebiotic chemical reaction mechanisms of our solar system can aid in the distinction between abiotic and biotic processes in Earth's early history, which remains poorly constrained. In addition, these mechanisms can provide insight into what can be considered an abiosignature versus a biosignature. Such insight is key when considering the inventory of organic compounds intrinsic to meteorites, since extant life on Earth easily and readily contaminates meteorites. Formation mechanisms proposed for the organic compounds identified in meteorites demonstrate that complex compounds can arise from nine simple precursors found in the interstellar medium: water (H₂O), ammonia (NH₃), hydrogen cyanide (HCN), carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄), hydrogen (H₂), nitric oxide (NO), and sulfur dioxide (SO₂). Here we combine the mechanisms proposed for the formation of synthetically produced prebiotic organic compounds, noting their links to organic compounds observed on meteorites, and discuss the current weaknesses in our understanding of reaction yields and/or missing or poorly constrained processes. This review and analysis provide a resource of current knowledge of laboratory-based experimental data and identify future directions that are, or we recommend should, be explored.