2/3 resonance). We have also confirmed the importance of these resonances through the numerical integration of The dynamical structure of the 2 / 3 resonance at small inclination is explored using numerical integrations of test particles both fictitious and ''real'' objects.
to compute the evolution of proper elements with time. The showed numerically that in the 2/3 basic features are related to the analytically computed geograresonance there are orbits that are stable 1 for at least 4 phy of secular resonances. This paper focuses on the existence byr. While this result was largely expected, an unexpected of slowly diffusing chaotic orbits, which escape from the 2 / 3 one was the discovery of several orbits that escape from resonance after billions of years. The origin of short-period the 2/3 resonance and encounter Neptune only after a very comets may be related to the existence of such orbits. We long time (ΟΎ1 byr; this phenomenon also exists for other numerically determine the rate at which 2/3 resonant objects regions of the Kuiper Belt). The existence of these orbits are delivered to close encounters with Neptune. From this result is very important in understanding the origin of shortwe estimate the number of comet-sized objects that should period (SP) comets. Indeed, since their dynamical lifetime presently be in the 2/3 resonance to explain the influx rate of is very short, the SP comets that we now observe must observed short period comets; the result of 10 8 to 10 9 seems to imply that 2/3 resonant bodies should be collisionally have left the Kuiper Belt just a few million years ago, many evolved.