The presence of exocometary gas in young (10-100 Myr) debris disks presents a unique opportunity to probe the composition of exocomets during the late stages of terrestrial planet formation. This is the evolutionary stage when ice-rich impacts are proposed to change the volatile environment of terrestrial planets, setting the stage for prebiotic chemistry. This action's goal is to use Exocometary Science as a unique tool for probing the composition of planetary systems in the crucial, last period of terrestrial planet formation. In particular, the action aimed to expand current observational approaches, focused on observations of carbon monoxide (CO) gas at millimetre wavelengths, to ultraviolet (UV) and (IR) wavelengths, in order to access atomic and yet unseen molecular species, including water, to probe the entire chemical variety of exocomets. To probe these yet unseen crucial species, the action aimed to exploit new and upcoming ground and space observatories. Additionally, the action aimed to study the origin of exocomet compositions - so far consistent with Solar System comets - and their link to a potentially common belt formation location in young protoplanetary disks. This was to be achieved through the REASONS survey dataset, an observational population study determining the location of tens of belts of exocomets.By achieving these goals, the action aimed to prepare for compositional inventories of exocomets, allowing us to put our Solar System comets into the broader context of extrasolar planetary systems, exoplanets and young disks, and providing a missing link in the study of planet formation and physical-chemical evolution.
Due to a change of institution ultimately driven by family reasons, the action had to be terminated after only 4 of the 24 months originally foreseen. This implies that only a small part of the planned work could be carried out.
