nothing to be done
More details today: investigations are focusing on the left rear wheel well of the Columbia, where the undercarriage is stored. It’s a weak spot in the otherwise unbroken wing surface, and NASA suspect that this area was damaged by ice or foam falling from the external fuel tank during takeoff. A break here would catch the wind and channel white-hot air inside, and temperature readings from the inner wing and side of the shuttle appear to confirm this. There are even photos of wing damage, published by NASA yesterday, though they show the upper wing, which doesn’t tell us much.
There are also reports that NASA knew that the damage would make re-entry hazardous, but did not tell the crew, allegedly because “there was nothing anyone could have done”. We can be certain that these allegations will be highly damaging, whether true or not. NASA, for better or for worse, is a political organization; George Bush has paid it almost no attention, never visiting the Johnson Space Centre in Houston during his eight years as Governor of Texas or his two years as President. They definitely have his attention now, and they might not like what happens next.