  Cosmological structure formation predicts that our galactic halo contains an
enormous hierarchy of substructures and streams, the remnants of the merging
hierarchy that began with tiny Earth mass microhalos. If these structures
persist until the present time, they could influence dramatically the detection
signatures of weakly interacting elementary particle dark matter (WIMP). Using
numerical simulations that follow the tidal disruption within the Galactic
potential and heating from stellar encounters, we find that neither microhalos
nor streams have significant impact on direct detection, 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.
