[FReepaholic]

>>...Didn't look like much of anything. Obviously fairly soft as it puffed into a cloud of frost(?) powder....<<

Unless that "frost" was what was left of dozens of tiles.

[Dan Day]

Unless that "frost" was what was left of dozens of tiles.

That's my thought as well -- pulverized ceramic (and the SS tiles are quite fragile) would look like that.

One thing I don't get -- if the most heat-critical parts of the shuttle (the nose, and the leading edges of the wings) are covered with a tough carbon composite material and not tiles, why not cover *all* of the heat-critical areas with the composite?