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Published August 10, 2017 | Submitted + Published
Journal Article Open

Destruction of Refractory Carbon in Protoplanetary Disks


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 ~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-α disk, where α = 0.01, carbon grains can be turbulently lofted into the destructive surface layers and depleted out to radii of ~3–10 au for 0.1–1 μm 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.

Additional Information

© 2017 American Astronomical Society. Received 2016 May 5. Accepted 2017 July 1. Published 2017 August 4. The authors thank the anonymous reviewer whose comments and suggestions improved this work. This material is based upon work supported by the National Science Foundation, via the Graduate Research Fellowship Program under grant No. DGE-1144469 and the Astronomy and Astrophysics Research Grants Program under grant No. AST-1514918.

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Submitted - 1707.08982.pdf

Published - Anderson_2017_ApJ_845_13.pdf


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August 21, 2023
August 21, 2023