TERRESTRIAL PLANET FORMATION DURING THE MIGRATION AND RESONANCE CROSSINGS OF THE GIANT PLANETS

Abstract

The newly formed giant planets may have migrated and crossed a number of\nmutual mean motion resonances (MMRs) when smaller objects (embryos) were\naccreting to form the terrestrial planets. We investigated the effects of the\nplanetesimal-driven migration of Jupiter and Saturn, and the influence of their\nmutual 1:2 MMR crossing on terrestrial planet formation for the first time, by\nperforming N-body simulations. These simulations considered distinct timescales\nof MMR crossing and planet migration. In total, 68 high-resolution simulation\nruns using 2000 disk planetesimals were performed, which was a significant\nimprovement on previously published results. Even when the effects of the 1:2\nMMR crossing and planet migration were included in the system, Venus and Earth\nanalogs (considering both orbits and masses) successfully formed in several\nruns. In addition, we found that the orbits of planetesimals beyond a ~1.5-2 AU\nwere dynamically depleted by the strengthened sweeping secular resonances\nassociated with Jupiter's and Saturn's more eccentric orbits (relative to\npresent-day) during planet migration. However, this depletion did not prevent\nthe formation of massive Mars analogs (planets with more than 1.5 times Mars'\nmass). Although late MMR crossings (at t > 30 Myr) could remove such planets,\nMars-like small mass planets survived on overly excited orbits (high e and/or\ni), or were completely lost in these systems. We conclude that the orbital\nmigration and crossing of the mutual 1:2 MMR of Jupiter and Saturn are unlikely\nto provide suitable orbital conditions for the formation of solar system\nterrestrial planets. This suggests that to explain Mars' small mass and the\nabsence of other planets between Mars and Jupiter, the outer asteroid belt must\nhave suffered a severe depletion due to interactions with Jupiter/Saturn, or by\nan alternative mechanism (e.g., rogue super-Earths).\n