Four Americans will land on the dark side of the moon within 10 years, as a stepping-stone to sending astronauts to Mars, according to the National Aeronautics and Space Administration.

A newly designed spacecraft will carry four astronauts to Earth’s only natural satellite, and ultimately will allow a human stay there of up to six months and serve as a weigh station for explorers headed to Mars.

“A lunar outpost just three days away from Earth will give us needed practice of ‘living off the land’ away from our home planet, before making the longer trek to Mars,” according to NASA’s Web site.

Astronauts aboard Apollo 8 first directly glimpsed the side of the moon that faces away from Earth – cut off from radio communication and covered in craters that will make for a challenging landing – in 1968, and future generations may touch down there by 2015, according to London’s Sunday Times.

“The samples they collect and the research they carry out will help solve many mysteries about the origins and composition of the moon and its suitability as a base,” the newspaper quoted NASA’s lunar lander project manager, John Connolly, as saying.

Ahead of the manned mission, robotic probes will be sent to photograph and map the moon’s surface, including the Lunar Reconnaissance Orbiter, set to launch in 2008, the Sunday Times reported. The program is part of President Bush’s “Return to the Moon” project and bears a price tag of about $98 billion, the paper said.