  We suggest that accretion of planet-bound dark matter by the Jovian planets,
and by hot-Jupiter exoplanets, could be a significant source of their internal
heat. The anomalously low internal heat of Uranus would then be explained if
the collision believed to have tilted the axis of Uranus also knocked it free
of most of its associated dark matter cloud. Our considerations focus on the
efficient capture of non-self-annihilating dark matter, but could also apply to
self-annihilating dark matter, provided the capture efficiency is small enough
that the earth heat balance constraint is obeyed.
