Shuttle probe focusing on mysterious object

Initially, NASA said it suspected the object might be frozen wastewater dumped overboard or an orbiting piece of space junk that the shuttle happened to encounter.

But on Tuesday, Air Force Brig. Gen. Duane Deal, a board member, discounted both possibilities and said the object almost had to have come from the shuttle itself.

"You or I could invent a dozen scenarios," Deal said. "It could have been something loose that separated, it could have been something inside the payload bay." It also could have been part of the left wing, where all of the overheating and other troubles developed during re-entry.

He described the object as about 1 foot by 1.3 feet in size and said it was flying in tandem with Columbia one day into the mission. It was within 50 feet of the shuttle and, within that first day, started separating farther and farther away until it burned up on re-entry three days later, he said.

The composition of the object is unknown, but it was lightweight and not dense, Deal said.

Columbia had just gone through a major maneuver in orbit on Jan. 17, about 24 hours into its flight, when the object popped out of nowhere, Deal said. That suggests it could have broken loose from the shuttle during the maneuver.<