  We make preliminary estimates to assess whether the recently reported flyby
anomaly can be attributed to dark matter interactions. We consider both elastic
and exothermic inelastic scattering from dark matter constituents; for
isotropic dark matter velocity distributions, the former decrease, while the
latter increase, the final flyby velocity. The fact that the observed flyby
velocity anomaly shows examples with both positive and negative signs, requires
the dominance of different dark matter scattering processes along different
flyby trajectories. The magnitude of the observed anomalies requires dark
matter densities many orders of magnitude greater than the galactic halo
density. Such a large density could result from an accumulation cascade, in
which the solar system-bound dark matter density is much higher than the
galactic halo density, and the earth-bound density is much higher than the
solar system-bound density. We discuss a number of strong constraints on the
hypothesis of a dark matter explanation for the flyby anomaly. These require
dark matter to be non-self-annihilating, with the dark matter scattering cross
section on nucleons much larger, and the dark matter mass much lighter, than
usually assumed.
