Search crews in Texas have found the space shuttle Columbia's data recorder, which could provide vital clues about what went wrong.
By Dr David Whitehouse
BBC News Online science editor
The Orbiter Experiments Recorder (OEX) stores key data about the shuttle's performance during re-entry.
Shuttle reassembled piece by piece
Officials say that the recorder was found almost intact. It may have suffered some heat damage.
The condition of the data tape inside the device is not yet known.
The OEX collects data on aerodynamic pressure, temperature, vibration and other variables. It is being taken to Nasa's Johnson Space Center for analysis.
If the data can be recovered, accident investigators will have a major source of information about Columbia's last moments - vital data about the aerodynamic forces acting on the spacecraft as it struggled to stay on course.
Seventeen years ago, divers recovered similar data tapes from the submerged wreckage of the shuttle Challenger. Investigators were able to extract valuable data from the tape despite extensive damage.
Only Columbia, Nasa's original space shuttle, has an OEX recorder.
It was originally part of the system used to collect data during the spacecraft's initial flights.
The OEX is not the same as Columbia's operational recorders, which contain additional data as well as voice traffic from the crew's intercom. They have yet to be found.
Investigators have not yet identified the cause of Columbia's destruction. All they can say at the moment is that superheated gas leaked into the orbiter's left wing causing it to disintegrate with the loss of all seven crewmembers on board.