The formation of a planet requires the steady accumulation of progressively larger particles 
and bodies, and so collisions must play a key role in the evolution of planetary systems. It 
is also clear that, as the average size of the bodies grows, individual collisions become 
rarer while at the same time becoming much more dramatic observationally. The heavily 
cratered lunar surface testifies to numerous planetesimal collisions during the heavy 
bombardment episode late in our solar system’s formation. However, the birth of the Moon 
itself, thought to have resulted from the collision of a Mars-sized body with the 
proto-Earth, must have been a truly spectacular event. Would the occurrence of such a 
catastrophic collision in another planetary system be observable directly? If so, we could 
begin to make a more concrete connection between planet-building collisional processes in 
our own and other planetary systems, thereby shedding additional light on this important 
early phase of planetary system evolution. In my presentation, I will review observational 
evidence suggesting that we may indeed be seeing the immediate aftermath of exosolar 
planetesimal collisions that in some cases are catastrophic. These observations include 
detection of spectroscopic signatures and multi-wavelength imaging of circumstellar disk 
asymmetries.