In the days after Columbia's destruction, NASA officials made their case: the foam couldn't have caused that kind of damage. It wasn't ice or metal that flew off the fuel tank. The left wing was not breached.
All that - and more - is back on the table and under the microscope, now that an investigation board is calling the shots.
In the 2½ weeks since Columbia shattered 38 miles above Texas, both NASA managers and board members have cautioned that the investigation is in continual flux, with new information turning up all the time. On Wednesday, NASA said the shuttle's nose landing gear was found in the east Texas woods.
But it is the board that has emphasized that everything is under consideration, no matter how seemingly irrelevant or obscure or unimaginable.
The fact that the accident investigation board has put NASA's discarded theories back on the table is "a combination of being thorough and being independent," said NASA's Steve Nesbitt, who is temporarily serving as the board spokesman.
The 10-member board - soon to gain a new member or two - is being scrutinized for signs of independence because it was chosen by NASA.
"The board wants to make sure every base is covered," Nesbitt said Wednesday. "They're not going to take NASA's word that everything is OK in a particular area."
"I don't like to use the word sabotage. But among the broad investigation that we're conducting, purposeful or willful damage is one of the things that we're looking at," the board's chairman, retired Navy Adm. Harold Gehman Jr., said Tuesday.
The fact that an Israeli war hero was among the seven astronauts killed is not driving that part of the investigation, Gehman insisted. "We are not doing it any more strongly because of the Israeli astronaut," he said.
The board said it would check the training and certification of the Columbia astronauts and flight controllers and also see whether budget pressures or poor management decisions contributed to the accident.
As for the hole in the wing, it could have developed inside or outside Columbia, the board said. Gehman said it's possible the explosive charges inside the left landing gear compartment may have gone off. Again, NASA dismissed that idea early on.
"Obviously, the NASA people in the immediate wake of the disaster have a tendency toward saying, 'We did everything right,' " said Steven Schneider, professor of aeronautics and astronautics at Purdue University. "It's human nature, especially if you knew the people who died. Then there's always, everybody has a tendency according to their interest to interpret the data in a way they like."
Schneider fears that may have happened with the in-house engineering analysis into the potential damage from the impact of tank debris during liftoff.
Within a week, NASA and its contractor engineers had concluded that the damage to Columbia's thermal protective layer, if any, was minimal and posed no safety threat. Shuttle managers signed off on the findings five days before the shuttle ended its science mission and headed home.
That entire evaluation is now being redone, in excruciating detail.
NASA has maintained from the start that even if it had known the insulating tiles or panels on the left wing were severely damaged, there was nothing the astronauts could have done to save themselves.
That, too, is back on the table.
By Marcia Dunn