  A weakly interacting dark-matter particle may be difficult to discover at an
accelerator because it either (1) is too massive, (2) has no standard-model
gauge interactions, or (3) is almost degenerate with other states. In each of
these cases, searches for annihilation products in the Galactic halo are useful
probes of dark-matter properties. Using the example of supersymmetric dark
matter, I discuss how astrophysical searches for dark matter may provide
discovery and mass information inaccessible to collider physics programs such
as the Tevatron and LHC.
