Pluto and Triton Interactions Between Volatiles and Dynamics

by: Rubincam, D. P.

ABSTRACT

Volatiles moving across the surfaces of Pluto and Triton can give rise to
interesting dynamical consequences. Conversely, measurement of dynamical
states can help constrain the movement of volatiles and interior structure
of both bodies. Polar wander may theoretically occur on both Triton and
Pluto. Triton's obliquity is low, so that the equatorial regions receive
more insolation than the poles. Hence there is a tendency for nitrogen ice
to sublime at the equator and condense at the poles, creating polar caps.
If the nitrogen supply is large enough, then these caps could move in
approximately 10(exp 5) years the global equivalent of 200 m of ice to
the poles. At this point the equatorial moment of inertia becomes larger
than the moment of inertia measured about the rotation axis, so that Triton
overbalances and becomes dynamically unstable. The satellite then undergoes
polar wander, restoring stability when the new equator contains the excess
matter. Hence the pole may be continually wandering. Neptune raises a perma-
nent tidal bulge on Triton, so that the satellite's surface is elongated
like a football, with the long axis pointing at Neptune. This is expected
to be the axis about which the pole wanders. Volatile migration would re-
surface the satellite to some depth and wandering would disturb leading
side trailing side crater statistics. Additional information is contained
in the original extended abstract.

Goddard Space Flight Center, 2001, Document ID 20010041277