Evolution in time of perihelion and aphelion for the Jupiter-mass planet (red curve) and the planet surviving in the HZ (blue curve). These results, obtained from Simulations 1, 6 and 15 of Scenario 2, are shown in the panels a–c, respectively. The horizontal dashed lines represent the inner and outer edges of the optimistic HZ. These planetary configurations remain dynamically stable for 1 Gyr.