37th DPS Meeting, 4-9 September 2005
Session 25 Planet and Satellite Formation
Oral, Tuesday, September 6, 2005, 2:00-3:50pm, Law LG19

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[25.07] Preventing Type II Migration of Jupiter and Saturn

A. Morbidelli, A. Crida (OCA), F. Masset (CEA)

Recent work [1][2][3] has advocated that the current structure of the Solar System can be explained if, at the end of the gas-disk phase, Jupiter and Saturn were closer to each other than their mutual 2:1 mean motion resonance, namely the ratio of their orbital periods was smaller than 2. Here we show that this planetary configuration may be a natural outcome of the evolution of the planets in the gas disk. Moreover, we argue that this configuration was necessary to prevent that Type II migration brought Jupiter and Saturn much closer to the Sun. Our work extends previous results [4], by exploring a wider set of initial conditions and disk parameters, and by using a new hydrodynamical code [5] that properly describes for the global viscous evolution of the disk. Initially both planets migrate towards the Sun, and Saturn's migration tends to be faster. As a consequence, they eventually end up locked in a mean motion resonance. If this happens in a `close' resonance (such as the 5:3, 3:2, 4:3 resonances) the gaps opened by the planets in the disk may overlap. This causes a drastic change in the torque balance for the two planets, which substantially slows down the planets' inward migration. If the gap overlap is substantial, planet migration may even be stopped or reversed. As the widths of the gaps depend on disk viscosity and scale height, this mechanism is particularly efficient in low viscosity, cool disks. The initial locking of the planets in a close resonance is a likely outcome if Saturn formed at the edge of Jupiter's gap. However, it is also possible if Saturn initially was beyond the 2:1 resonance with Jupiter, because the fast migration of Saturn often causes the planet to jump across this resonance.

[1] Tsiganis et al., Nature, 435, 459 2005 [2] Morbidelli et al., Nature, 435, 462 2005 [3] Gomes et al., Nature, 435, 466 (2005) [4] Masset and Snellgrove, MNRAS, 320, 55 (2001) [5] Crida, Masset and Morbidelli, in preparation.

The author(s) of this abstract have provided an email address for comments about the abstract: morby@obs-nice.fr

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Bulletin of the American Astronomical Society, 37 #3
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