  Predicting signals in direct dark matter (DM) detection experiments requires
an understanding of the astrophysical structure of the local halo. Any
uncertainty in this understanding will feed directly into all experimental
results. However our terrestrial experiments are in a position to study this
same astrophysical dependence, and in fact represent our only probe of the
local halo on sub-milliparsec scales. This is best achieved in the case of WIMP
dark matter if directionally sensitive experiments are feasible, but requires
novel parameterizations of the velocity distribution to make model independent
claims. For axions the prospects are much greater, haloscopes would be able to
make better measurements of the local DM distribution than astrometric probes.
