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T. Guillot (OCA), R. Hueso (Univ. Pais Vasco)
It has been proposed that the enrichment in noble gases found by Galileo in Jupiter's atmosphere can be explained by their delivery inside cold planetesimals. We propose instead that this is a sign that the planet formed in a chemically evolved disk and that noble gases were acquired directly in gaseous form during the envelope capture phase.
We show that the combined settling of grains to the disk midplane in the cold outer layers, the condensation of noble gases onto these grains at temperatures below 20-30K, and the evaporation from high disk altitudes effectively lead to a progressive, moderate enrichment of the disk. The fact that noble gases are vaporized from the grains in the hot inner disk regions (e.g. Jupiter formation region) is not a concern because a negative temperature gradient prevents convection from carrying the species into the evaporating region. We show that the ~2 times solar enrichment of Ar, Kr, Xe in Jupiter is hence naturally explained by a slow formation of the planet and capture of the moderately enriched disk gas on viscous timescales (Myrs).
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.