Disk evolution, element abundances and cloud properties of young gas giant planets
Ch.Helling (1), P.Woitke (1), P.B.Rimmer (1), I.Kamp (2), W.-F.Thi (3), R.Meijerink (2,4) (1 – University of St Andrews, 2 – Kapteyn Astronomical Institute Groningen, 3 – Laboratoire d’Astrophisique de Grenoble, 4 – Leiden Observatory)
(Submitted on 18 Mar 2014)
We discuss the chemical pre-conditions for planet formation, in terms of gas and ice abundances in a protoplanetary disk, as function of time and position, and the resulting chemical composition and cloud properties in the atmosphere when young gas giant planets form. Large deviations between the abundances of the host star and its gas giants seem likely to occur if the planet formation follows the core-accretion scenario. These deviations stem from the separate evolution of gas and dust in the disk, where the dust forms the planet cores, followed by the final run-away accretion of the left-over gas. ProDiMo protoplanetary disk models are used to predict the chemical evolution of gas and ice in the midplane. We find that cosmic rays play a crucial role in slowly un-blocking the CO, where the liberated oxygen forms water, which then freezes out quickly.
Therefore, the C/O ratio in the gas phase is found to gradually increase with time, in a region bracketed by the water and CO ice-lines. In this regions, C/O is found to approach unity after about 5 Myrs, scaling with the cosmic ray ionisation rate. We then explore how the atmospheric chemistry and cloud properties in young gas giants are affected when the non-solar C/O ratios predicted by the disk models are assumed. The DRIFT cloud formation model is applied to study the formation of atmospheric clouds under the influence of varying primordial element abundances and its feedback onto the local gas. We demonstrate that element depletion by cloud formation plays a crucial role in converting an oxygen-rich atmosphere gas into carbon-rich gas when non-solar, primordial element abundances are considered as suggested by disk model.
Comments: 32 pages, accepted for publication in the OA journal ‘Life’, Special issue ‘Planet Formation and the Rise of Life’. Life (ISSN 2075-1729)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:1403.4420 [astro-ph.EP] (or arXiv:1403.4420v1 [astro-ph.EP] for this version)
Submission history From: Christiane Helling
[v1] Tue, 18 Mar 2014 11:56:40 GMT (523kb,D)
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