Until now most people thought the disaster was caused by some space debris hitting the shuttle's wing.
New evidence
However, this fresh discovery has made some investigators think again.
The tile is covered in mysterious orange marks. A spokesman for an independent inquiry into the crash says they definitely weren't caused by the heat of re-entry.
Wreckage from the shuttle has been found all over America
Insulation foam which came off and hit the shuttle during its launch is the same colour as the marks. This might mean the tile was loosened by the foam during launch.
If it came off in re-entry, it may have caused the huge rise in temperature in the wing that most people think is the reason for the disaster.
A spokesman for NASA said: "The data and twisted metal are speaking to us. We're just developing ears to hear."
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