Nasa is planning to build a permanently occupied base on the moon. It is being described as the first step towards creating settlements in space. Building work will start after a new series of flights to the moon begins in 2020. Experts say they hope it will eventually become a stepping stone for future missions to Mars and other planets. The habitat, most likely at the lunar north pole, will serve as a science outpost as well as a testbed for technologies needed for future travel (Advertisement) to planets. "We're going for a base on the moon," Scott 'Doc' Horowitz, Nasa's associate administrator for exploration, said. Plans for what the base will look like and what astronauts would do there have yet to be determined. Nasa has also not projected a date when the base would go into operation. The moon's polar sites are preferred to equatorial regions because of more moderate temperatures and longer periods of sunlight. This is critical for the solar-powered electrical systems Nasa plans to develop. Scientists also suspect the poles have resources such as hydrogen, ice and other materials that could be used for life support. "It's exciting," said Nasa deputy administrator Shana Dale. "We don't know as much about the polar regions." The US had already announced plans to develop new spacecraft to travel to the moon and land on its surface for the first time since the last Apollo flight there in 1972. It also plans to provide a communications system linking Earth and the moon.