Abstract

We investigate the role of tidal interaction in the formation and evolution of binary near-Earth asteroids. To tidally evolve in their ~10 Myr dynamical lifetime, near-Earth binaries with 1 km-scale primaries created via a spin-up mechanism must be orders of magnitude weaker mechanically than their main belt counterparts. If 1 km-scale near-Earth binaries are instead formed in the main belt prior to injection into the near-Earth region, both the time available for tidal evolution and the mechanical strength increase to values comparable to main belt binaries. Aside from the inherent diffculty in deriving material properties from tidal evolution due to the necessity of choosing the evolution timescale, other perturbations and torques can affect the mutual orbit and rotation states of a near-Earth binary system during tidal evolution, including: orbit about an non-spherical primary, excitation by close planetary (or solar) encounters, angular momentum addition/removal by the YORP effect, and other possible methods of angular momentum transfer. We are incorporating these effects into our modeling to evaluate the extent that these interactions have shaped the properties we observe among the near-Earth binary population.