What's the best way to test a Mars rover before launch? Well it turns out the easiest way is to build a test planet here on Earth.
Scientists in Hertfordshire have recreated a small piece of the Mars surface which has the same sand and rocks as the red planet, and is about the size of a basketball court.
It will be used to test systems on the Mars rover that Europe will send to the planet in four years time.
ExoMars, as it's known, will be a six-wheeled robot on a mission to find signs of past or present life.
Nel's been to the converted warehouse to find out how it works.