Presentation #107.05 in the session Modern Theories of Planetesimal Formation.
The population of interstellar objects are diagnostic both of the formation conditions of their planetary disks, and of the metallicity of the stellar environment in which they were born. When planetesimals are dispersed from their system of origin, this record is carried with them. As objects that then travel through the Solar System, they offer the prospect of placing experimental constraints on Galactic history — with a very different lens to that of Galactic archaeology. Using the EAGLE cosmological simulations and models of protoplanetary formation, our modelling predicts an ISO population with a bimodal distribution in their water mass fraction: objects formed in low-metallicity, typically older, systems have a higher water fraction than their counterparts formed in high-metallicity protoplanetary disks, and these water-rich objects comprise the majority of the population. The population of ISOs in galaxies with different star formation histories will have different proportions of objects with high and low water fractions.