Photochemistry of interstellar ice forming complex organic molecules

Astrochemistry is a well-established multidisciplinary field devoted to the study of atoms and molecules in space. Although many astrochemists study molecules in the gas phase and reproduce their abundances by modelling the physical conditions of the interstellar medium, the microscopic dust particles floating in the interstellar medium also deserve the attention of the community. Radiation and thermally driven processes taking place on the bare dust, and particularly on dust particles covered by icy mantles, are mimicked in the laboratory. In addition to water, interstellar ice contains other simple species. In this Review we present our current knowledge on ice photochemistry and thermal processing that ultimately leads to the formation of complex organic molecules. Numerous complex organic molecules are of astrobiological interest and match those present in comets and asteroids. Upon impact of these minor bodies, water and complex organic molecules could have been delivered to the early Earth, which might have been vital for the first prebiotic reactions.