A piece of foam shot at the leading edge of a model shuttle wing Thursday cut a 22-inch gap in the surface and knocked loose a seal -- a finding termed "significant" by a Columbia Accident Investigation Board official.

The test is the first of several that investigators probing the space shuttle Columbia disaster plan to conduct to try to determine what caused the craft to break up February 1, killing all seven astronauts aboard.

One of the leading theories into the accident has been that a piece of foam insulation that hit Columbia's wing during liftoff damaged insulation tiles or the leading edge of the wing, eventually leading to the shuttle's disintegration during re-entry.

In Thursday's test, a foam piece weighing just 1.67 pounds was fired at 531 mph at the mock wing, which was made of fiberglass -- a material 2.5 times stronger than the reinforced carbon carbon (RCC) used on Columbia's wing.

The foam left a 22-inch opening on the wing, ranging in thickness from that of a dime to more than a quarter inch. It also knocked loose a T-seal, which helps protect the wing.

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