The object floated away after a series of routine pre-landing procedures in which the crew tested the steering jets, a test which often shakes loose objects off of the spacecraft. The procedures also include working the craft’s flaps. A commentator for the space program’s TV service said that the entry flight director, Richard Jones, called in imagery experts and structural and mechanical experts to, as the commentator put it, “hammer this one flat” and make sure there is no concern for landing on Saturday.

If a serious problem had been discovered, the crew could have take the shuttle back to the International Space Station, which it separated from on Wednesday, under what is known as the “safe haven” plan, so that mission managers could determine whether to repair the craft or attempt to send another shuttle as a rescue vehicle.

Image The vertical stabilizer on the shuttle Discovery on Friday. The shuttle crew discovered a small protrusion on the rudder section of the stabilizer. Credit... NASA TV/Associated Press

At 11:30, Colonel Virts radioed to the crew that the issue had been resolved. The object floating away from the craft was one of three clips that attach to the rudder and protects against heating during ascent. It has no function during reentry, and so its loss presents no problem for the craft or crew, he said. As for the protrusion, it is a normal part of the rudder assembly that was exactly the same as it had been during launching, Colonel Virts said, but might have appeared to protrude because the rudder was now being seen at a slightly different angle than before.

Rob Navias, a commentator on the space program’s NASA TV service that can be viewed online, said that mission control was now pressing ahead with its previous plans for landing. Discovery is scheduled to land as early as Saturday at 11:15 a.m., though problems like rain, low clouds over the landing strip or high winds could lead mission managers to delay the landing to later on Saturday or put it off to Sunday or even Monday.