[John Jorsett]

The picture you posted looks like the surface area where the tiles are attached. Those whitish burned places look like the tiles...sort of burned or melted. The squares appear to be the places where other tiles where at one time.

I think you're exactly right. I saw a televison program about the shuttle one time, and it showed the process of applying the tiles. The orbiter was laid out with this sort of gridwork to mark where the tiles go.

[seams2me]

That photo was the one that made me cry, even moreso than the sole of the shoe, and the helmet.