The discovery of numerous Earth-sized planets on close orbits around other stars compels investigations of how they formed, challenges traditional models of planet formation, and provides an opportunity to study such objects in detail. This program will bring together experts in exoplanet demographics, protoplanetary disks, models of disks and planet formation, and meteoritics to address four key questions: (1) what is the nature of close-in rocky planets and their atmospheres? (2) do they form in-situ or migrate inwards after forming further out? (3) what are the governing parameters that could vary between star systems? and (4) why are there no analogous planets around the Sun?

Answering these questions requires a better understanding of the structure, dynamics, and composition of protoplanetary disks. The inner disk can be resolved by infrared interferometers like GRAVITY, diagnostic atomic and molecular lines observable by HST or JWST emanate from inner disk gas. These observations can be interpreted with the aid of high-resolution, 3-D disk models, while analyses of meteorites and samples from asteroids provide comparative information on conditions, processes, and timescales in the proto-Solar System disk. The goal of this program is to address these questions and forge tools and information from different disciplines into a predictive model of close-in planet formation. It will stimulate collaboration and encourage knowledge integration among participants, and harness the invitation process and preparation period to foster great diversity in scientific culture and cross-talk between disciplines.