  Detecting dark matter as it streams through detectors on Earth relies on
knowledge of its phase space density on a scale comparable to the size of our
solar system. Numerical simulations predict that our Galactic halo contains an
enormous hierarchy of substructures, streams and caustics, the remnants of the
merging hierarchy that began with tiny Earth mass microhalos. If these bound or
coherent structures persist until the present time, they could dramatically
alter signatures for the detection of weakly interacting elementary particle
dark matter (WIMP). Using numerical simulations that follow the coarse grained
tidal disruption within the Galactic potential and fine grained heating from
stellar encounters, we find that microhalos, streams and caustics have a
negligible likelihood of impacting direct detection signatures implying that
dark matter constraints derived using simple smooth halo models are relatively
robust. We also find that many dense central cusps survive, yielding a small
enhancement in the signal for indirect detection experiments.
