Ah ha! You are the first person to bring up the shard, well done :D Notice on the above image how there is a white layer and a gray layer of overlapping bands. The shard is likely a piece of the white layer. So I guess I'm a bit incorrect in my OP when I say I'm talking about the outermost layer, when I actually mean both the gray overlapping area and the white coating are 1km combined. Edit: I updated the OP to be more specific, thanks mate!