Originally posted by HackenTrollen
I've seen this before, it was confirmed to be a dirty spot on the camera.
Where was it confirmed? Although I totally believe it. I take pictures a lot and this kind of thing happens when there is dirt on the lens or even a raindrop could do it. Heck, it could have even been a bug just sitting there. Happens all the time, just normally it isn't available to the general internet public.
Still, makes a neat image!