DDA 2015 – The Evolution of the Grand Tack’s Main Belt through the Solar System’s Age

This is one of a series of notes taken during the 2015 meeting of the AAS Division on Dynamical Astronomy, 3-7 May, at CalTech. An index to this series (all the papers presented at the meeting) is here.

Rogerio Deienno (National Institute for Space Research)

Abstract

The Asteroid Belt is marked by the mixture of physical properties among its members, as well as its peculiar distribution of orbital eccentricities and inclinations. Formation models of the Asteroid Belt show that its formation is strongly linked to the process of terrestrial planet formation. The Grand Tack model presents a possible solution to the conundrum of reconciling the small mass of Mars with the properties of the Asteroid Belt, providing also a scenario for understanding the mixture of physical properties of the Belt objects. Regarding the orbital distribution of these objects, the Grand Tack model achieved good agreement with the observed inclination distribution, but failed in relation to the eccentricities, which are systematically skewed towards too large values at the end of the dynamical phase described by the Grand Tack model. Here, we evaluate the evolution of the orbital characteristics of the Asteroid Belt from the end of the phase described by the Grand Tack model, throughout the subsequent evolution of the Solar System. Our results show the concrete possibility that the eccentricity distribution after the Grand Tack phase is consistent with the current distribution. Finally, favorable and unfavorable issues faced by the Grand Tack model will be discussed, together with the influence of the primordial eccentricities of Jupiter and Saturn. Acknowledgement: FAPESP.

Notes

  • Asteroid belt:
    • formation process halted before formation of a planet due to Jupiter
    • so-called “Grand Tack” model
      • Walsh et al. 2011
      • Jup &  Sat migrate inwards, Saturn faster
      • inward stops, outward begins
      • but fails to explain a lot
        • current MB structure different from Grand Tack predictions
        • especially dist. in $e$, also $a$ ($i$ not bad)
  • This work
    • Num int 5 planets & 10,000 test particles, 4.5 Gyr
    • ICs: Grand Tack
    • Mercury integrator, 10-day time step — expensive
    • E-belt (Bottke et al. 2012) results @ 0.4 Gyr (planetary instability)
    • at 0.4 Gyr, reset planets to their current orbits
    • $\rightarrow$ asteroid belt of today — almost
      • much better match to observed $a$-$e$-$i$ distributions
      • lost somewhat more asteroids than observed
    • Influence of primordial eccentricities ofJup & Saturn
      • destabilizes MMRs
      • $\rightarrow$ constraints on primordial eccentricities
    • see also: Nesvorny & Morbidelli 2012 AJ 144:117

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