The sun is obviously just out of shot above the lens and this is almost certainly a flare, being diametrically opposite it.
I see from the EXIF data that the aperture was f/8, so you would normally expect to see the aperture blades, the fact you can't suggests three possibilities:
a) It is a very peculiar flare that only appears at certain very precise angles of sun image hitting a round aperture inside the lens, that is before the iris
b) The (I assume) curved blades of the iris are cut to be perfectly circular at f/8, or
c) There was a circular drop of something on the front element/filter, which acted as an additional lens and caused the flare.
b) or c) are most likely, the patterning perhaps favours c) as the cause
or the alien
Cheers,