[waterlesscloud]

The best theory I've seen is that it's a piece of foil tape that's crumbled in the harsh cold. Hopefully that's all it is.

[ceejayoz]

There does appear to be a screw hole with a missing screw, though: http://postimage.org/image/ouvupuniz/full/

[3rd3]

http://www.youtube.com/watch?v=mjEgTuCFLU4&t=0m36s

[ceejayoz]

Nice find!