**DDA2001, April2001**

*Session 11. Small Icy Things*

Wednesday, 10:10-11:30am
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## [11.02] Diffusive Dynamics of Scattered Disk Objects with Large Perihelia

*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 10^{7} years, 1 objects
will survive 4 x 10^{9} 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.

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