This comes as officials in Texas and Louisiana have appealed for more help in searching for debris from the shuttle.
Tiles may have fallen off
More than a thousand bits of wreckage have already been found, but there's many more spread out over a huge area.
Nasa has revealed more information about Columbia before it crashed. Some heat-resistant tiles designed to protect the craft from the heat of re-entry into the earth's atmosphere may have been falling off.
Nasa officials said the left side of the shuttle started getting hotter and hotter as it got closer to landing.
This could be because of the tiles falling off or becoming uneven, but said they were also investigating lots of other bits of information too, including huge amounts of computer data sent back by the shuttle in its final moments.
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