Grand tack hypothesis

In planetary astronomy, the grand tack hypothesis proposes that Jupiter formed at a distance of 3.5 AU from the Sun, then migrated inward to 1.5 AU, before reversing course due to capturing Saturn in an orbital resonance, eventually halting near its current orbit at 5.2 AU. The reversal of Jupiter's planetary migration is likened to the path of a sailboat changing directions (tacking) as it travels against the wind.^[1]

The planetesimal disk is truncated at 1.0 AU by Jupiter's migration, limiting the material available to form Mars.^[2] Jupiter twice crosses the asteroid belt, scattering asteroids outward then inward. The resulting asteroid belt has a small mass, a wide range of inclinations and eccentricities, and a population originating from both inside and outside Jupiter's original orbit.^[3] Debris produced by collisions among planetesimals swept ahead of Jupiter may have driven an early generation of planets into the Sun.^[4]