Theoretical eccentricities e′ adopted by test particles after a close encounter with Fom c, which has set them on an orbit with semi-major axis compatible with the orbit of Fom b. In the left panel, the 5:2 MMR will constrain the semi-major axis to a_MMR and will allow a test particle to cross the chaotic zone of Fom c for values of eccentricity e between 0.2 and 0.8, hence the configurations (a′,e′) allowed for a particle after its encounter with Fom c are comprised between two curves. In the right panel, close-encounters occur in the chaotic zone of Fom c, with initially low-eccentricity particles (0 <e< 0.05), but here the semi-major axis can span values from the inner edge of the chaotic zone to the semi-major axis of Fom c. Therefore, there is a total of four curves on this plot, two curves for each boundary value in semi-major axis, but because of the small span in eccentricity, these are very close and appear as a single curve. The horizontal red dotted line figures the minimum eccentricity required for an orbit to be compatible with that of Fom b.