DDA 36th Meeting, 10-14 April 2005
Session 11 Orbits and Orbit Evolution II: Moons
Oral, Wednesday, April 13, 2005, 9:35am-12:15pm

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[11.07] Dynamical Instability and Accretion in Systems of Closely-Spaced Inner Moons

J.A. Meyer (Stanford University), J.J. Lissauer (NASA Ames Research Center)

We have numerically integrated the 13 largest Uranian regular satellites, including mutual gravitation, for a period of three million years. We used the hybrid symplectic integrator in the Mercury package (Chambers 1999, MNRAS 304, 793). The simulations include the five classical moons as well as the eight largest inner moons. The Voyager-discovered satellites' masses are ill-constrained, due to the lack of observed gravitational perturbations. The masses are estimated using the observed radii combined with an assumed density; for moons of unknown radii, the albedo was assumed to be similar to that of nearby moons. We simultaneously simulate these uncertainties in mass and explore the dynamical interactions of closely-spaced satellite systems by allowing the common density of the non-classical moons to run from 0.1 to 30 g/cc.

For our initial integrations, which neglected Uranus's oblateness, the 3 Myr interval was sufficient time for one to six collisions, depending on the density assumed for the inner moons. Each collision was modeled as completely inelastic. While Uranus's outer classical moons appear stable for the duration of the integrations, the inner moons are much less stable and collide on a timescale well within the solar system's lifetime. Results of calculations including the effects of Uranus's oblateness will also be presented. Preliminary results indicate that including the J2 and J4 moments leads to later collision times in the low density range.

First collision times agree qualitatively with the results of Duncan and Lissauer (Icarus 125, 1, 1997). Our novel results include the study of subsequent collisions and implications for the formation history of the Uranian satellites.

The author(s) of this abstract have provided an email address for comments about the abstract: meyerj@stanford.edu

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Bulletin of the American Astronomical Society, 37 #2
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