It is the groove ( better seen on the yellow pad) where the backing plate contacted the pad. The foam seems to be seperating. Only two passes on the car with #9.
Sometimes Meguiar's pads don't hold up too well. As I recall, they're working on some new, improved ones. *I* would get a bunch of Lake/CMA/TOL or Griot's pads. Even if you just stick with the Meg's ones, I suggest you keep plenty on hand and just replace them when you need to.
Moved away form this huh? Heh heh, then you must be pretty sensible for a Viper owner J/K, of course!
Lucky you to avoid the crappy weather we're having! I'm starting to sorta LIKE the winter (must be going nuts), but it IS tough on the detailing efforts, and the good cars are probably tired of sitting.