How Jupiter's Two-Phase Gas-Driven Migration Shaped the Inner Solar System
Résumé
Accretion simulations cannot adequately reproduce the terrestrial planets, in particular Mars' small mass [1]. Currently, the best solution to this problem assumes that the terrestrial building blocks were initially concentrated in a narrow annulus from 0.7-1 AU [2]. These initial conditions could have been sculpted by Jupiter's two-phase migration in the gaseous Solar Nebula: Jupiter first migrated inward due to standard type 2 torques, then back outward once Saturn grew and was trapped in 2:3 resonance [3]. If the turnaround point or "tack" occurred when Jupiter was at 1.5 AU then the inner disk of material would be truncated at 1 AU, forming a small Mars (Figure 1). In this scenario, the asteroid belt was first emptied and then re-filled by Jupiter: S-type asteroids (red in Figure 1) originated between 1-3 AU and C-types (blue) originated between the giant planets and beyond Neptune [4]. In the absence of migration, primitive C-type asteroids represent a plausible source for Earth's water [5]. In the context of the 'grand tack' model [4], this same population may still deliver water to the growing Earth: for every C-type planetesimal injected into the asteroid belt, ~10 were scattered onto eccentric orbits that intersect the terrestrial planet- forming region. These scattered C-types can deliver several oceans of water to the growing Earth.