Abstract

The composition of planets is largely determined by the chemical and dynamical evolution of the disk throughout planetesimal formation and growth. To account for the evolution of the disk during planetesimal formation, we couple models of protoplanetary disk chemistry and dynamics with a model of planetesimal formation. We then follow the growth of these planetesimals into terrestrial planets with N-body simulations of late stage planet formation. We find that our model produces carbon enriched planets over a wide range of semi-major axes for disks that are initially enhanced in carbon (C/O > 0.8). Furthermore, we find that planetesimal formation in the outer disk leads to the depletion of oxygen, or equivalently, an enhancement of the C/O ratio in the disk. As the disk material is transported inwards, the C/O ratio will continue to be enhanced up to the point where carbon rich solids will condense out. This mechanism can produce carbon rich planets close to the star for disks with initial C/O ratios lower than 0.8. This suggests that if many of the known close in terrestrial exoplanets formed in situ, there are likely more carbon rich planets than initially thought.

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