Investigators now have a working theory on how the space shuttle Columbia broke up.
New frame-by-frame analysis points to a chunk of foam from Columbia's exterior fuel tank that struck the leading edge of the shuttles left wing. Investigators believe that strike was the most plausible cause of Columbia's demise.
They say it opened a hole that allowed super-heated air to enter the shuttle during re-entry. A series of foam impact tests will soon get underway at a research lab in San Antonio to confirm the theory.
As for finding shuttle debris, so far search crews have covered an area the size of Rhode Island and have recovered only one-third of the shuttle.