CAPE CANAVERAL, Fla. (AP) - 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 extra time 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.

“The question is: What is it? Is it something benign? … Or is it something more critical we should pay attention to?” said Wayne Hale, space shuttle program manager. “We want to make sure we’re safe to land before we commit to that rather incredible journey through the Earth’s atmosphere.”

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