35th Meeting of the AAS Division on Dynamical Astronomy, April 2004
Session 6 Asteroids \& TNOs
Oral, Thursday, April 22, 2004, 2:15-6:50pm,

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[6.02] Asteroid Fission and Final Rotation Rates

D.J. Scheeres (University of Michigan)

The rotational angular momentum of asteroids can increase due to planetary flybys or non-gravitational torques such as YORP. If the angular momentum of an asteroid becomes large enough, it may disrupt and form a binary (or more) system. If this occurs during a planetary flyby, the rotation rate of the asteroid may be significantly larger than its disruption limit. On the other hand, if this occurs due to a slow process such as YORP, the asteroid may be very close to its disruption limit. In either case, we can think of the asteroid as having undergone ``fission'' in that it is now disassembled into two or more pieces. The analogy with fission occurs as a large amount of potential energy, previously locked up in the self-potential of the asteroid, becomes available for exchange and interaction with the kinetic energy of the system. Thus, what previously was a system with no internal dynamics (a rotating single body) is turned into a system with non-trivial internal dynamics. Such newly formed binaries can be very unstable and may mutually escape after only several orbits, separating into two non-interacting asteroids.

This talk will discuss constraints that can be placed on these binaries after such a disruption occurs. Specifically, bounds can be placed on the final rotation rates of the separated asteroids, and in some cases these rotation rates can be quite small, indicating that slow rotators can arise as end products of asteroid fission. An important observation is that the physics of these bounds is controlled by a scalar, and not vector, quantity and thus may be able to replicate the distribution statistics reported in (A. Harris, Icarus 156, 184--190, 2002).

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Bulletin of the American Astronomical Society, 36 #2
© 2004. The American Astronomical Soceity.