I was running through some images of a Dornier 328Jet that I had shot at Boeing Field.  I was zoomed in close to check for image sharpness when my eye caught the inside of the nozzle of the engine nacelle.  There was an interesting pattern on the inside.  Judging by the layout of the staining, I think the mixer in the exhaust results in varying deposition of material on the walls.  This is the sort of thing that really appeals to me and probably no one else but it is my blog!