  We consider the ability of three models - impacts, captures, and collisional
cascades - to account for a bright cloud of dust in Fomalhaut b. Our analysis
is based on a novel approach to the power-law size distribution of solid
particles central to each model. When impacts produce debris with (i) little
material in the largest remnant and (ii) a steep size distribution, the debris
has enough cross-sectional area to match observations of Fomalhaut b. However,
published numerical experiments of impacts between 100 km objects suggest this
outcome is unlikely. If collisional processes maintain a steep size
distribution over a broad range of particle sizes (300 microns to 10 km),
Earth-mass planets can capture enough material over 1-100 Myr to produce a
detectable cloud of dust. Otherwise, capture fails. When young planets are
surrounded by massive clouds or disks of satellites, a collisional cascade is
the simplest mechanism for dust production in Fomalhaut b. Several tests using
HST or JWST data - including measuring the expansion/elongation of Fomalhaut b,
looking for trails of small particles along Fomalhaut b's orbit, and obtaining
low resolution spectroscopy - can discriminate among these models.
