NASA set to launch new 'Maven' Mars craft

NASA is launching a new Mars explorer later, which, it is hoped, will work out how the red planet changed.

Mars was once warm and wet but is now cold and dry.

The spacecraft, known as Maven, (Mars Atmosphere and Volatile Evolution) will blast off from Cape Canaveral in Florida.

Lead scientist Michael Meyer says there is a big unanswered question around what happened to Mars, which was once able to support microbial life.