Département de chimie moléculaire

How could life emerge on an originally inorganic Earth ? This is the main question faced in the field of prebiotic chemistry. In order to solve this issue, two main, and not incompatible, hypotheses have been made. An endogenous synthesis one, based on the theory that building blocks of life were synthesized in the atmosphere of the early Earth and/or in prim-itive oceans, and an exogenous delivery one, according to which those building blocks were synthesized in space and then brought to Earth by comets and asteroids. In this contribution, based on state-of-the-art quantum chemistry computations, both hypotheses will be considered. First, possible gas-phase formation routes in the interstellar medium for two molecules of pre-biotic interest will be investigated: glycolaldehyde (HOCH₂CHO), the simplest sugar-related molecule, able to ease the formation of more complex sugars and formamide (H₂NCHO), a possible precursor that might be able to link the appearances of metabolism and genetics. Andthen, thanks to a synergy between experimental and theoretical chemistry, a potential way of forming mercaptoacetaldehyde (HSCH₂CHO), a possible prebiotic precursor of cysteine, will be explored in the peculiar conditions of the early Earths ocean.