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[15.22] Equilibrium configurations and the Roche limit for spinning ellipsoidal soil-like asteroids

I. Sharma (ITG, DAMTP, Cambridge University), J. T. Jenkins, J. A. Burns (TAM, Cornell University)

Recent research has suggested that asteroids might be particle aggregates held together by self-gravity alone. This has important implications on the possible equilibrium shapes of spinning asteroids. As in the case of spinning fluid masses, which only form Jacobi ellipsoids, Maclaurin spheroids, etc., not all shapes and spins may be compatible with a granular rheology. To study this issue, we take an asteroid to be an ellipsoid and its interior to be composed of a rigid-plastic, cohesion-less soil.

Using an approximate volume-averaged procedure, it is possible then to derive regions in spin-shape parameter space where equilibrium solutions can exist. The results that we find are the same as those reported by Holsapple (2000), but are obtained with much less effort. It is also possible to investigate the dynamics of such spinning asteroids and attempt to recover the results of Richardson et al. (2004), who determined equilibrium shapes of smooth spherical aggregates by numerically studying their passage into equilibrium. As a final application of this approximate procedure, the Roche limit for a satellite tidally interacting with a central planet is derived, and is in complete agreement to the one obtained by Davidsson (2001) .

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.