A voyage from dark clouds to the early Earth

Abstract

Stellar nucleosynthesis of heavy elements, followed by their subsequent release into the interstellar medium, enables the formation of stable carbon compounds in both gas and solid phases. Spectroscopic astronomical observations provide evidence that the same chemical pathways are widespread both in the Milky Way and in external galaxies. The physical and chemical conditions—including density, temperature, ultraviolet radiation and energetic particle flux—determine reaction pathways and the complexity of organic molecules in different space environments. Most of the organic carbon in space is in the form of poorly-defined macromolecular networks. Furthermore, it is also unknown how interstellar material evolves during the collapse of molecular clouds to form stars and planets. Meteorites provide important constraints for the formation of our Solar System and the origin of life. Organic carbon, though only a trace element in these extraterrestrial rock fragments, can be investigated in great detail with sensitive laboratory methods. Such studies have revealed that many molecules which are essential in terrestrial biochemistry are present in meteorites. To understand if those compounds necessarily had any implications for the origin of life on Earth is the objective of several current and future space missions. However, to address questions such as how simple organic molecules assembled into complex structures like membranes and cells, requires interdisciplinary collaborations involving various scientific disciplines. Introduction Life in the Universe is the consequence of the increasing complexity of chemical pathways which led to stable carbon compounds assembling into cells and higher organisms.