DPS 2001 meeting, November 2001
Session 31. Cometary Nuclei and Dynamics
Oral, Chairs: D. Scheeres, C. Lisse, Thursday, November 29, 2001, 2:40-4:20pm, Regency E

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[31.07] Dynamical evolution of comet nucleus rotation

D.J. Scheeres (Univ. of Michigan, Ann Arbor), V.V. Sidorenko (Keldysh Inst. of Applied Math., Moscow), A.I. Neishtadt, A.A. Vasiliev (Space Research Inst., Moscow)

The rotational dynamics of outgassing cometary nuclei are investigated analytically using dynamical systems theory. We develop a general theory for the averaged evolution of a comet nucleus rotation state assuming that the nucleus is a spheroid (either prolate or oblate) and that the outgassing torques are a function of solar insolation and heliocentric distance. The resulting solutions are a function of the comet outgassing properties, its heliocentric orbit, and the assumed distribution of active regions on its surface.

We find that the long-term evolution of the comet nucleus rotation is a strong function of the distribution of active regions over its surface. Specifically, we find that a comet nucleus with a uniformly active surface will tend towards a rotation state with a nutation angle of ~ 55 degrees and an angular momentum perpendicular to the sun-perihelion direction. Conversely, a comet nucleus with an isolated active region will tend towards a zero nutation angle with its symmetry axis and angular momentum aligned parallel to the sun-perihelion direction. For active surface regions between these extremes we find 4 qualitatively different dynamical outcomes. In all cases, the theory predicts that the comet nucleus angular momentum will have a secular increase, a phenomenon that could contribute to nucleus splitting of active comets.

These results can be used to discriminate between competing theories of comet outgassing based on a nucelus' rotation state. They also allow for a range of plausible a priori constraints to be placed on a comet's rotation state to aid in the interpretation of its outgassing structure.

This work was supported by the NASA JURRISS program under Grant NAG5-8715. AIN, AAV and VVS acknowledge support from Russian Foundation for Basic research via Grants 00-01-00538 and 00-01-0174 respectively. DJS acknowledges support from the PG&G program via Grant NAG5-9017.

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

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