CAPE CANAVERAL, Fla. — NASA postponed the return of Atlantis for at least a day and examined the shuttle for damage that could prevent it from making the journey home after a mysterious object apparently fell off the ship in orbit Tuesday.
Space agency officials wanted to establish whether the object was a vital piece of the shuttle — such as the tiles that protect it from the blowtorch heat of re-entry — and whether it harmed the spacecraft when it fell away.
Officials were not optimistic they would be able to identify the object, since the possibilities were almost endless, ranging from harmless ice to crucial thermal protection tiles. But the leading candidate was a plastic space-filler placed between the thermal tiles.
"We want to make sure we're safe to land before we commit to that rather incredible journey through the Earth's atmosphere," said Wayne Hale, space shuttle program manager.
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The shuttle has enough supplies to stay in space until Saturday while engineers on the ground figure out whether it can safely return to Earth.
Contingency plans
The space agency did not rule out the possibility of a spacewalk to make repairs or, if the spacecraft is too damaged, sending Atlantis's six crew members to take refuge in the international space station and await rescue by another shuttle — a scenario that NASA has been developing ever since the Columbia disaster in 2003.
The landing time was reset from today to early Thursday.
The incident came near the end of what had been a nearly flawless mission devoted to restarting construction of the space station for the first time since the Columbia tragedy 3 1/2 years ago.
Mission Control spotted the baffling object — the size of which was not immediately determined — with a video camera in the shuttle's cargo bay. The object may have come out of the cargo bay early Tuesday, but officials were not certain.
The object floated near the shuttle in the same orbit for a while, slipping farther and farther away until it was just a dark speck in NASA video beamed down to Earth.
A few minutes after NASA made the midday decision to delay the landing, Atlantis astronaut Dan Burbank photographed what appeared to be another small object floating away from the spacecraft. But NASA spokesman James Hartsfield said: "They're not the same thing."
Later in the day, Hale said the object likely was a plastic bag that drifted out of the cargo bay.
NASA engineers said they think the first object may have shaken loose from the shuttle during the firing of jets in preparation for landing. "Think about driving over potholes," Hale said.
