Tidal dissipation in rubble pile asteroids
Abstract We develop a simple scaling argument for frictional dissipation in rubble pile asteroids, parameterized as an effective dissipation factor Q. This scaling is combined with a prediction (Goldreich, P. Sari, R. 2009. Tidal evolution of rubble piles. Astrophys. J. 691, 54 60) for the tidal response amplitude, parameterized by the Love number k2. We compare the combined scaling with k2/Q values inferred from asteroid binaries in which the semi major axis is determined by a balance between tidal dissipation and the binary YORP (or BYORP) effect (Jacobson, S.A. Scheeres, D.J. 2011. Long term stable equilibria for synchronous binary asteroids. Astrophys. J. Lett. 736, L19) The k2/Q scaling matches the inferred values if dissipation is confined to a regolith layer of thickness 30 m, similar to the available asteroid regolith thickness estimates. The scaling suggests a regolith thickness that is independent of (or decreases slightly with) increasing asteroid radius; this result is consistent with at least one model of regolith generation via impacts.
Icarus