Contribution Invited Talk
Understanding the formation of formamide (NH$_2$CHO), a key precursor of prebiotic chemistry
One of the major questions regarding the origin of life on Earth is whether the original mechanism that led from simple molecules to life was connected to metabolism or to genetics, both intimately linked in living beings. Formamide (NH$_2$CHO) contains the four most important elements for biological systems, and it has recently been proposed as a precursor of both metabolic and genetic material, suggesting a common chemical origin for the two mechanisms. Moreover, recent experiments have shown that the four nucleobases present in RNA might have naturally formed from formamide during the Late Heavy Bombardment, which further stresses its key role in the synthesis of biogenic molecules.
Formamide was first detected in molecular clouds more than four decades ago. Despite this, dedicated observational studies have started only very recently, as its potential role as a precursor of prebiotic chemistry has become more evident. These studies report the presence of formamide in massive hot molecular cores, one low-mass hot corino, and the comet Hale-Bopp. In the past months, the IRAM Large Program ASAI, dedicated to astrochemical studies of star-forming regions, has revealed new discoveries of NH$_2$CHO in several solar-type protostars and outflow shock spots. The presence of formamide in such a variety of star-forming environments, as well as on a Solar System comet, opens the possibility of an exogenous delivery onto a very young Earth more than 4 billion years ago.
In this talk, we will present the different observational studies of formamide that have been carried out in the past years, with a particular emphasis on our new ASAI results. We will discuss the different chemical pathways that have been recently suggested to explain its formation, which include gas-phase as well as gas-grain reactions, and review the observational constraints brought by ASAI. Finally, we will stress the importance of joining efforts with experts on both theoretical and experimental chemistry in order to make progress. Further dedicated observational studies, particularly with the interferometers ALMA and NOEMA, will be crucial in order to place constraints on the various formation routes so far proposed.