Corrosion suggested in shuttle crash Weakened wing may have been vulnerable to impact of debrisBy James ObergSPECIAL TO MSNBC.COM IN RECENT DAYS, NASA officials have expressed their frustrated bafflement over the observed debris impact on Columbia’s left wing. They have repeated studies made during the flight and still come up with results that show the worst-case damage is still far short of a mortal wound that could have prompted the catastrophic failure of the wing. If the falling insulating foam were the triggering event, some additional factor or factors must have been present,...