The ultimate plan is to build a base and keep astronauts there permanently: a step on from the permanent presence in space afforded by the International Space Station and a practice run for any future adventures to Mars.
Nasa announced plans to go back to the moon earlier this week and gave details of the rockets and vehicles it plans to use to get humans back there by 2018, almost 50 years after the Apollo astronauts last walked on it.
Exactly what form the rudimentary moon base will take is still in the earliest stages of planning, but Nasa did give some clues. Because taking equipment up into space is so prohibitively expensive, scientists want the astronauts to build as much as they can with materials on the moon itself. The priority for the next decade in space technology, then, will be producing mini-factories which will be able to process the raw ingredients available on the moon.
The day after the space agency unveiled its plans, it announced a $250,000 prize for scientists and inventors to come up with a machine that can excavate the most soil and deliver it to a collector. The digger will be used by robots. They will be dispatched to the dark craters at the moon's poles to find out if there is water ice there, a source of rocket fuel, oxygen and water to keep crew and equipment going.
The diggers will also mine ilmenite, a mineral from which astronauts can extract oxygen, hydrogen and helium. This could produce air and water, while the flammable gases could be burned to generate electricity.
Nasa said the lunar base would provide a "huge head start in getting to Mars. A lunar outpost just three days away from Earth will give us needed practice of 'living off the land' away from our planet, before making the longer trek to Mars."
