The Earth and other rocky bodies in the inner solar system contain significantly less carbon than the primordial materials that seeded their formation .
These carbon-poor objects include the parent bodies of primitive meteorites , suggesting that at least one process responsible for solid-phase carbon depletion was active prior to the early stages of planet formation .
Potential mechanisms include the erosion of carbonaceous materials by photons or atomic oxygen in the surface layers of the protoplanetary disk .
Under photochemically generated favorable conditions , these reactions can deplete the near-surface abundance of carbon grains and polycyclic aromatic hydrocarbons by several orders of magnitude on short timescales relative to the lifetime of the disk out to radii of \sim 20–100+ au from the central star depending on the form of refractory carbon present .
Due to the reliance of destruction mechanisms on a high influx of photons , the extent of refractory carbon depletion is quite sensitive to the disk ’ s internal radiation field .
Dust transport within the disk is required to affect the composition of the midplane .
In our current model of a passive , constant- \alpha disk , where \alpha = 0.01 , carbon grains can be turbulently lofted into the destructive surface layers and depleted out to radii of \sim 3–10 au for 0.1- \SI 1 \micro \metre grains .
Smaller grains can be cleared out of the planet-forming region completely .
Destruction may be more effective in an actively accreting disk or when considering individual grain trajectories in non-idealized disks .