  Despite strong evidence for the existence of large amounts of dark matter
(DM) in our Universe, there is no direct indication of its presence in our own
solar system. All estimates of the local DM density rely on extrapolating
results on much larger scales. We demonstrate for the first time the
possibility of simultaneously measuring the local DM density and interaction
cross-section with a direct detection experiment. It relies on the assumption
that incoming DM particles frequently scatter on terrestrial nuclei prior to
detection, inducing an additional time-dependence of the signal. We show that
for sub-GeV DM, with a large spin-independent DM-proton cross section, future
direct detection experiments should be able to reconstruct the local DM density
with smaller than 50% uncertainty.
