  As the first dark matter objects gravitationally condense, a density cusp
forms immediately at every initial density maximum. Numerical simulations and
theoretical arguments suggest that these prompt cusps can survive until the
present day. We show that if dark matter is a thermally produced weakly
interacting massive particle, many thousands of prompt cusps with individual
masses similar to that of the Earth may be present in every solar mass of dark
matter. This radically alters predictions for the amount and spatial
distribution of dark matter annihilation radiation. The annihilation rate is
boosted by at least an order of magnitude compared to previous predictions,
both in the cosmological average and within galaxy-scale halos. Moreover, the
signal is predominantly boosted outside of the centers of galactic halos, so
alternative targets become significantly more attractive for indirect-detection
searches. For example, prompt cusps present new opportunities to test the dark
matter interpretation of the Galactic Center gamma-ray excess by searching for
similar spectral signatures in the isotropic gamma-ray background and
large-scale cosmic structure.
