Carbon-rich planet formation in a solar composition disk

Mohamad Ali-Dib, Olivier Mousis, Jean Marc Petit, Jonathan I. Lunine

    Research output: Contribution to journalArticlepeer-review


    The C to O ratio is a crucial determinant of the chemical properties of planets. The recent observation of WASP 12b, a giant planet with a C/O value larger than that estimated for its host star, poses a conundrum for understanding the origin of this elemental ratio in any given planetary system. In this paper, we propose a mechanism for enhancing the value of C/O in the disk through the transport and distribution of volatiles. We construct a model that computes the abundances of major C- and O-bearing volatiles under the influence of gas drag, sublimation, vapor diffusion, condensation, and coagulation in a multi-iceline 1+1D protoplanetary disk. We find a gradual depletion in water and carbon monoxide vapors inside the water's iceline, with carbon monoxide depleting slower than water. This effect increases the gaseous C/O and decreases the C/H ratio in this region to values similar to those found in WASP 12b's day side atmosphere. Giant planets whose envelopes were accreted inside the water's iceline should then display C/O values larger than those of their parent stars, making them members of the class of so-called carbon-rich planets.

    Original languageEnglish (US)
    Article number125
    JournalAstrophysical Journal
    Issue number2
    StatePublished - Apr 20 2014


    • planets and satellites: atmospheres
    • planets and satellites: composition
    • planets and satellites: formation
    • protoplanetary disks

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science


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