The chunk of foam insulation that struck Columbia during liftoff — the most evident glitch in the mission — does not appear to have caused the shuttle to break apart as it reentered the atmosphere, NASA officials said.A top NASA official effortlessly picked up a large piece of the material Wednesday to demonstrate to reporters that it is too light and flakes off too easily to have led to the destruction Saturday of a 173,000-pound spacecraft the size of a DC-9 airliner.‘‘It does not make sense that a piece of (foam) would be the root cause of the Columbia and the crew. We don’t believe it’s the chunk of foam,’’ said Ron Dittemore, the NASA’s space shuttle programme manager.Investigators have been flown in to California, where the shuttle apparently first experienced problems, and where hardware may have begun falling off.In Washington, Michael Kostelnik, deputy associate administrator said the shuttle suffered some sort of ‘‘anomaly’’ over California. He said, the plasma draped over the spacecraft as it raced over California changed colours at one point, suggesting that the craft may have struck an object. NASA engineers say they are weighing the possibility that the space shuttle’s heat-resistant tiles may have been damaged by space junk or a tiny space pebble, known as a micrometeorite.The California Highway Patrol has received 60 calls about possible shuttle debris.NASA has long been concerned about the potential danger to the space shuttle and space station from thousands of pieces of space junk from old satellites and rockets and tiny shards of space rock.In fact, shuttles are regularly struck by objects and NASA regularly repairs the damages. ‘‘Even something as small as a fleck of paint, when it’s travelling at really high speeds, could cause significant damage,’’ said an expert.Meanwhile, remains of the seven crew members, discovered scattered amid the wreckage in Texas and Louisiana, were flown Wednesday to a Delaware Air Force base. (LATWP)
