  We investigate a scenario where the recently discovered non-thermal hard
X-ray emission from the Ophiuchus cluster originates from inverse Compton
scattering of energetic electrons and positrons produced in weakly interacting
dark matter pair annihilations. We show that this scenario can account for both
the X-ray and the radio emission, provided the average magnetic field is of the
order of 0.1 microGauss. We demonstrate that GLAST will conclusively test the
dark matter annihilation hypothesis. Depending on the particle dark matter
model, GLAST might even detect the monochromatic line produced by dark matter
pair annihilation into two photons.
