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M. Holman (Harvard-Smithsonian Center for Astrophysics), T. Grav (Institute of Theoretical Astrophysics, U. Oslo), B. Gladman (Observatoire de la Cote d'Azur)
Roughly 40 transneptunian objects with large semimajor axes (a>50 AU) and eccentricities (e>0.4) have been identified since the discovery of 1996 TL66 (Luu et al. 1997). This scattered disk population, first predicted in the numerical integrations of Torbett (1989) and Torbett and Smoluchowski (1990) and later studied extensively by Duncan and Levison (1997), not only contains a substantial fraction of the mass of the transneptunian region but also serves as a reservoir of material to be delivered to the interplanetary region. For the scattered disk to be an effective reservoir, a fraction of its population must be long-lived. As pointed out by Duncan and Levison (1997), while the median dynamical lifetime of an object from first Neptune scattering is a mere 4.5 x 107 years, 1 objects will survive 4 x 109 years. The perihelia of these survivors are raised to a point where gravitational interactions with Neptune are weak.
Here, we examine the diffusive dynamics of scattered disk objects with large perihelia. Extending the work of Torbett (1989) and Torbett and Smoluchowski (1990), we show that the borders of the chaotic region of the scattered disk, in semimajor axis and eccentricity, are only approximately described by lines of constant perihelion. Indeed, at larger semimajor axes the chaotic zone extends to larger values of perihelion. This alters the type and range of scattered disk orbits believed to be accessible through diffusive dynamics. Extending the work of Wisdom (1980) and Malyshkin and Tremaine (1999), we show that the chaotic zone associated with the scattered disk results from the overlap of high-order mean motion resonances.
This research has been supported in part by the NASA Planetary Geology and Geophysics program.