Nasa is building robots that can dig up Martian soil and convert it into rocket fuel.

The machines will strip water from the soil and convert it into methane - a compound that has been tipped to power the rockets of the future.

They could solve a major problem facing Nasa's deep space plans: How to keep rockets light enough to fly while still carrying enough fuel to get to and from Mars.

Nasa plans to send manned missions to Mars in the early 2030s.

But before humanity takes its first step on the red planet, the space agency will send a fleet of unmanned vehicles to test the habitability of its arid, dusty surface.

The new robots, nicknamed 'dust-to-thrust factories', could form part of these key early trips, according to one Nasa software engineer.

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