One this day one year ago, Columbia failed to return home. Seven courageous astronauts were lost in the skies over Texas that morning. Mission details are on the STS-107 web site.
The report of the Columbia Accident Investigation Board is available online.
The Board determined that physical and organizational causes played an equal role in the Columbia accident – that the NASA organizational culture had as much to do with the accident as the foam that struck the Orbiter on ascent.