Mountain Halo

On the way back from the mall on Friday afternoon, we noticed this - an aeroplane of some sort circling behind our mountain, but leaving a trail that looked like a halo from our angle. It was actually above a distant mountain range, and as soon as we got a bit closer it was hidden by our lump of rock.

Oh for a zoom and a decent-resolution camera.... :) But it was pretty cool. Wonder how many other people on the road noticed it?

(the dot on the 2nd pic is dirt on the windscreen...)