  The amount of dust present in circumstellar disks is expected to steadily
decrease with age due to the growth from micron-sized particles to
planetesimals and planets. Mature circumstellar disks, however, can be observed
to contain significant amounts of dust and possess high dust-to-gas ratios.
Using HD 163296 as our case study, we explore how the formation of giant
planets in disks can create the conditions for collisionally rejuvenating the
dust population, halting or reversing the expected trend. We combine N-body
simulations with statistical methods and impact scaling laws to estimate the
dynamical and collisional excitation of the planetesimals due to the formation
of HD 163296's giant planets. We show that this process creates a violent
collisional environment across the disk that can inject collisionally produced
second-generation dust into it, significantly contributing to the observed
dust-to-gas ratio. The spatial distribution of the dust production can explain
the observed local enrichments in HD 163296's inner regions. The results
obtained for HD 163296 can be extended to any disk with embedded forming giant
planets and may indicate a common evolutionary stage in the life of such
circumstellar disks. Furthermore, the dynamical excitation of the planetesimals
could result in the release of transient, non-equilibrium gas species like H2O,
CO2, NH3 and CO in the disk due to ice sublimation during impacts and, due to
the excited planetesimals being supersonic with respect to the gas, could
produce bow shocks in the latter that could heat it and cause a broadening of
its emission lines.
