EXODOSS · EXOplanet Diversity and the Origin of the Solar System

The ongoing discovery of ever-more Earth-like exoplanets raises the question how these planets form. Answering this question requires a breakthrough in our understanding of terrestrial planet formation, since this topic has previously been studied almost exclusively in the context of the Solar System and with an emphasis on the late-stage giant-impact phase. However, recently, a window into the very earliest stages of planet formation has opened through radio observations of protoplanetary discs around young stars that reveal large reservoirs of mm-sized pebbles. In EXODOSS, I will model the full planetary growth process, starting from these primordial pebbles, in order to improve our fundamental understanding of terrestrial planet formation. In order to do so, I will develop a first-of-its-kind GPU-accelerated N-body simulator that models planetary growth and composition in a protoplanetary disc where angular momentum is transported by disc winds. The code will follow the growth of the first pebbles and km-sized planetesimals to larger protoplanets, up to the late dynamical evolution of fully-grown planetary systems. Additional supporting hydrodynamical simulations will provide much needed accurate prescriptions for the evolution of the protoplanetary disc and for the accretion rates of pebbles and gas onto the cores and atmospheres of young protoplanets. Taken together, I will establish a self-consistent model of planet formation capable of addressing how Earth-like planets form, with results that can be confronted against dynamical and compositional constraints from the Solar System and the growing population of well-characterized Earth-like exoplanets. These theoretical investigations are needed in the broader context of humanity's search for habitable Earth-like exoplanets in our galaxy, our desire to understand their formation, and as a first step in tracing the origin of the elements, such as water, required for the development of life as we know it.