What does it mean for the other shuttles?
The shuttle fleet will be grounded while what happened is investigated.

After the Challenger disaster in 1986 the shuttle fleet was grounded for more than two years.

But there's lots of pressure to fly again as soon as possible - the shuttles are the main supply ships for the International Space Station (ISS).

What does it mean for the whole American space programme?
President George W Bush has vowed that US space exploration will continue despite the tragic loss of Columbia and the deaths of its crew.

What about the crew on the space station?
The shuttles were regular visitors to the ISS.

But the station is also visited by unmanned supply vessels.

The crew have enough supplies to last for several months.

And even with its shuttles grounded, the astronauts aboard the space station could be picked up using Russian spacecraft.

Can the ISS crew make a quick escape?
If necessary, a Russian Soyuz "lifeboat" spacecraft attached to the space station could bring the three astronauts onboard back to Earth at a moment's notice.