Limits of the inert region in the (a, q) plane. Each column corresponds to a different value of the initial ecliptic inclination (see titles). The colour scale represents the maximum possible orbital variations in 4.5 Gyrs: the top row shows the variation of ecliptic inclination, and the bottom row shows the variations of perihelion distance (see labels on the right). The black level corresponds to a variation of 5^o in inclination (top row) or 10 au in perihelion distance (bottom row). Below the black level, the region can be considered inert. See text for the white symbols.