The Chemical Evolution in Open Space: A Link to the Origin of Life

Abstract

It is now well known that carbonaceous chondrites contain large quantities of prebiotic molecules, including amino acids, carbohydrates, and heterocyclic bases of nucleic acids. It has become evident that the chemical evolution proceeds under conditions of open space on the small bodies of the Solar system, which surface serves as a huge chemical reactor. The extraterrestrial origin of these prebiotic molecules has been established on the basis of diversity, molecular structure, and isotopic composition. The molecular composition of a meteorite’s organics resembles abiotic processes governed by physicochemical processes that occurred on the parent bodies, including asteroids. The synthesis of soluble compounds in carbonaceous chondrites consists of a multistep process in which organic precursors were formed in the interstellar cloud, incorporated with many volatiles into icy planetesimals, and upon aqueous processing produced the variety of compounds which can form very complex organics in such harsh environments. We show experimentally that the solid mixtures of biologically significant compounds (nucleosides and amino acids) produce more complex compounds when they are exposed to either vacuum UV photons or ionizing radiation.