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, 112 (14), 4214-7

Jupiter's Decisive Role in the Inner Solar System's Early Evolution


Jupiter's Decisive Role in the Inner Solar System's Early Evolution

Konstantin Batygin et al. Proc Natl Acad Sci U S A.


The statistics of extrasolar planetary systems indicate that the default mode of planet formation generates planets with orbital periods shorter than 100 days and masses substantially exceeding that of the Earth. When viewed in this context, the Solar System is unusual. Here, we present simulations which show that a popular formation scenario for Jupiter and Saturn, in which Jupiter migrates inward from a > 5 astronomical units (AU) to a ≈ 1.5 AU before reversing direction, can explain the low overall mass of the Solar System's terrestrial planets, as well as the absence of planets with a < 0.4 AU. Jupiter's inward migration entrained s ≳ 10-100 km planetesimals into low-order mean motion resonances, shepherding and exciting their orbits. The resulting collisional cascade generated a planetesimal disk that, evolving under gas drag, would have driven any preexisting short-period planets into the Sun. In this scenario, the Solar System's terrestrial planets formed from gas-starved mass-depleted debris that remained after the primary period of dynamical evolution.

Keywords: Solar System formation; extrasolar planets; planetary dynamics.

Conflict of interest statement

The authors declare no conflict of interest.


Fig. 1.
Fig. 1.
Orbital distribution of sub-Jovian extrasolar planets. A collection of transiting planet candidates with radii R<5R (where R is an Earth radius unit), detected by the Kepler mission is shown. The radial distance away from the center of the figure represents a logarithmic measure of the planetary semimajor axis, such that the origin corresponds to the Sun’s surface. The sizes of the individual points represent the physical radii of the planets. Further, the points are color-coded in accordance with multiplicity. The orbits of the terrestrial planets are also shown. Despite observational biases inherent to the observed distribution (e.g., transit probability, detectability) that work against detection of planets at increasing orbital radii, the raw contrast to our own Solar System is striking.
Fig. 2.
Fig. 2.
Orbital evolution of planetesimals embedded in the solar nebula, under the effects of a migrating Jupiter. As Jupiter moves inward from 6 AU to 1.5 AU, planetesimals are swept up by mean motion resonances (MMRs). A shows the increase in the planetesimal eccentricity associated with resonant transport. Note that at the end of Jupiter’s trek, there exists a strong enhancement in the planetesimal density at the Jovian 2:1 MMR. B depicts the preferential population of Jupiter’s interior MMRs. Each planetesimal in the simulation is color-coded in accord with its initial condition, and the resultant curves track the orbital excursions of the small bodies as Jupiter’s orbit shrinks. Jupiter’s return to ∼5 AU is not modeled directly. In the presented simulation, we assumed a planetesimal size of s=100 km. Similar figures corresponding to s=10 km and s=1,000 km can be found in Supporting Information.
Fig. 3.
Fig. 3.
Orbital decay of a hypothetical compact system of super-Earths (an analog of the Kepler-11 system) residing within the terrestrial region of the primordial Solar System. Following a collisional avalanche facilitated by Jupiter’s migration, a population of planetesimals (here assumed to be ground down to s=100 m) decays inward and resonantly shepherds the interior planets into the star. Planetesimal orbits are shown with colored lines, while the planetary orbits are shown with black and gray lines. Specifically, the planetary semimajor axes are shown in black, while the perihelion and aphelion distances are shown in gray. Note that the results shown herein are largely independent of planetesimal size, as long as the planetesimals are small enough to drift inward on a timescale smaller than ∼1 My due to aerodynamic drag.

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