Research ArticleASTEROIDS

The empty primordial asteroid belt

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Science Advances  13 Sep 2017:
Vol. 3, no. 9, e1701138
DOI: 10.1126/sciadv.1701138
  • Fig. 1 Outcome of our simulations.

    (Top) Semimajor axis–mass distribution of the terrestrial planets that formed in our simulations. The black squares represent the actual terrestrial planets. The clustering of planets at ~0.05 M simply represents the starting embryo mass. Although some planets on Mars-like orbits were far larger than the actual one, we only included simulations with good Mars analogs in determining the abundance of implanted S-types. (Bottom) Semimajor axis–eccentricity and inclination distribution of S-type asteroids implanted from the terrestrial planet region. All planetesimals from the end of the simulations are shown, and the implanted ones are solid. The shaded region represents the main asteroid belt, defined here as having perihelion distance q > 1.8 AU, eccentricity e < 0.3, and inclination i < 25°.

  • Fig. 2 Radial distribution of implanted asteroids.

    S-types are 100-km planetesimals implanted onto stable orbits within the main belt from 159 simulations of terrestrial planet formation. The total mass in S-types was determined using only those simulations that matched Mars’ mass and did not strand embryos in the asteroid belt (30), but the distribution of all implanted asteroids was used, as we found no systematic difference. The C-types are 100-km planetesimals implanted during Jupiter and Saturn’s rapid gas accretion (31), calibrated to contain 1.7 times as much total mass as the S-types (3).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/9/e1701138/DC1

    Initial conditions

    Additional details about S-type implantation

    Implantation of C-type asteroids driven by the gas giants’ growth

    fig. S1. Surface density profile of the underlying gas disc profile used in our simulations, drawn from hydrodynamical simulations (18).

    fig. S2. How 10 asteroids from different simulations were implanted into the belt.

    fig. S3. Efficiency with which planetesimals were implanted into the main asteroid belt in our simulations.

    fig. S4. Snapshots in the evolution of a simulation in which the giant planets’ growth implants planetesimals from the Jupiter-Saturn region as C-type asteroids.

    References (5457)

  • Supplementary Materials

    This PDF file includes:

    • Initial conditions
    • Additional details about S-type implantation
    • Implantation of C-type asteroids driven by the gas giants’ growth
    • fig. S1. Surface density profile of the underlying gas disc profile used in our simulations, drawn from hydrodynamical simulations (18).
    • fig. S2. How 10 asteroids from different simulations were implanted into the belt.
    • fig. S3. Efficiency with which planetesimals were implanted into the main asteroid belt in our simulations.
    • fig. S4. Snapshots in the evolution of a simulation in which the giant planets’ growth implants planetesimals from the Jupiter-Saturn region as C-type asteroids.
    • References (54–57)

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