Airbus has built a giant sand pit in Stevenage to mimic the surface of Mars.
The indoor terrain, about the size of a basketball court, will be used to test systems on the rover that Europe will send to the Red Planet in 2018.
ExoMars, as it is known, will be a six-wheeled robot tasked with finding signs of past or present life.
The UK division of Airbus Defence and Space will assemble the rover from parts built across member states of the European Space Agency (Esa).
But it has the specific role also of developing the vehicle's autonomous navigation system.
The great distance between Earth and Mars means the robot cannot be controlled in real time; commands take tens of minutes to cross the space between the planets.
Instead, ExoMars will be given a destination to reach, and its onboard cameras and computer will then work out the most appropriate route, avoiding large boulders and potential fissures in the ground.
Euro-Russian mission to Mars
- ExoMars rover set for launch in May 2018
- Proton rocket will send it on its way
- Russians also building landing system
- Touchdown should occur in January 2019
- Rover will look for biosignatures on Mars
- Initial mission duration will be 218 Mars days
The new 'Mars yard' is being used to develop the necessary algorithms.
'We need to verify the performance, to check that the algorithms and the processes that we're using will actually work - will be fit for purpose to deal with the conditions and obstacles we expect to find on Mars,' said Dr Ralph Cordey from Airbus.
The sandpit will play a critical role also in testing the rover's drive systems.
Like previous vehicles sent to the Red Planet, ExoMars will be based on a free-moving, rocker-bogie suspension that allows it to climb over small rocks.
This equipment will be provided by robotics experts at MacDonald Dettwiler and Associates in Canada (Canada is a co-operating member state of Esa).
Various prototypes already at Stevenage have been trying out the new 'Marscape'.
The lessons learned will be built into the eventual 'flight' model - the actual vehicle that is sent to Mars.
This itself will never see the Mars yard. It will be assembled in a new 'cleanroom' at the Airbus factory to ensure it is kept spotless, and free from any Earthly contamination that could confuse its instruments when they go hunting 'biosignatures' on Mars.
Once Airbus has assembled the flight model, it will be sent to Thales Alenia Space in Turin, Italy, where its payload of scientific instruments will be added.
The key UK science contribution is the PanCam imaging system developed by a team under the leadership of Prof Andrew Coates at the Mullard Space Science Laboratory.
The current US rover, Curiosity, has wowed us with its pictures from Gale Crater. ExoMars hopes to do the same.
'Curiosity can see a lot, but PanCam will be able to see a much larger region in its field of view,' Prof Coates explained.
'It can also zoom in and view sections in great detail with our high-resolution camera. With that we'll be able to narrow down where to drill to search for signs of life.'
Precisely where on the Red Planet ExoMars will go has yet to be decided.
The project is holding its first landing-site selection meeting this week in Madrid, Spain.
Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos