NASA workers inspecting space shuttle Atlantis this week discovered that a tiny piece of space debris had punched a hole in a radiator panel during the shuttle's recent mission, but officials said the damage never endangered the crew.

The debris struck a panel that extends from payload bay doors on the shuttle.

It wasn't clear exactly what the object was, but it did not hit the sensitive tiles or thermal panels that help protect the shuttle when it returns to Earth.

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The impact left a hole about one-tenth of an inch in diameter, NASA reported Thursday on its Web site.

The damage "didn't endanger the spacecraft or the crew, nor did it affect mission operations," NASA said.

The radiators were brought inside the bay before the shuttle's landing last month, so the damaged area did not encounter searing heat during re-entry through Earth's atmosphere.

In 2003, space shuttle Columbia broke apart during re-entry when superheated gases entered a hole in the shuttle's wing. A breakaway chunk of hard foam from Columbia's external fuel tank had punctured that wing during liftoff.

After the Columbia disaster, NASA began intense inspections of the shuttle, both by camera during liftoff and by the astronauts once in space.