US: Nasa plans to put humans on the moon for the first time since the early 1970s, establishing a permanent manned base camp on its southern pole within 20 years.
In the initial phase of the plan, four-person crews would spend a week at a time on the moon until power and other supplies are in place for a permanent base. The settlement would ultimately become a staging post for astronauts engaged in further exploration of the solar system, providing hydrogen and oxygen drawn from the lunar surface to make water and rocket fuel.
Scott Horowitz, Nasa's chief of lunar exploration, said the decision to resume manned missions to the moon followed meetings with hundreds of scientists, potential international partners and space businesses over the past year.
"The lunar base will be a central theme in our going forward plan for going back to the moon in preparation to go to Mars and beyond," he said. "It's a very, very big decision and it's one of the few where I've seen the scientific community and the engineering community actually agree on anything."
The agency declined to estimate the cost of the project, but suggested it could be jointly funded with international partners and private space businesses. Nasa officials have discussed the plan with the European Space Agency and the national space agencies of Australia, Britain, Canada, China, France, Germany, India, Italy, Russia, South Korea and Ukraine.
The moon's southern pole is almost always sunlit, making it the best place on the lunar surface to harness solar energy. It is surrounded by craters holding volatile gases, including helium-3, which can be used for nuclear power and offers commercial potential.
Nasa will send a robot lander to the moon in 2010 to scout for possible sites for the base, which could be located near the Shackleton Crater, named after the Co Kildare-born Antarctic explorer Ernest Shackleton.
Mr Horowitz said Nasa hoped to develop an all-purpose lunar lander that would touch down anywhere on the moon's surface and would be the first stage in establishing a base camp.
"The nickname I use for the lander is, it's a pick-up truck. You can put whatever you want in the back. You can take it to wherever you want. So you can deliver cargo, crew, do it robotically, do it with humans on board. These are the types of things we're looking for in this system."
Mr Horowitz added that having a base camp did not mean every moon landing by humans would use it.
The option remains for some missions to go to equatorial regions, as the Apollo missions did in the 1970s, or to the far side of the moon, where some space agencies want to install a bank of powerful telescopes.