NASA has taken the first tentative steps in rekindling agency interest in the Moon. As part of its New Frontiers spacecraft plans, NASA has requested proposals for a South Pole-Aitken (SPA) Basin Sample Return project.

Past robotic spacecraft orbiting the Moon have spotted what appear to be super-cold stashes of water ice. These reservoirs are seemingly tucked away in craters, hidden from the Sun's thawing rays. The Moon's South Pole is thought by many scientists to be loaded with tons of water ice. If available, this treasure trove resource could help support return-to-the-Moon expeditions.

To do so, processing machines would convert the water ice into oxygen, drinkable water, and rocket fuel. By churning out these products, living off the Moon might more easily become a way of life for future explorers.

Taking a hard look at prospective landing sites at the lunar South Pole is Philip Stooke, a space scientist at the Departments of Geography and Physics and Astronomy at the University of Western Ontario in London, Ontario, Canada.

"The lunar South Pole is interesting for its proximity to the South Pole-Aitken basin and the potential for volatile materials -- including water -- in perpetually shaded areas," Stooke said. Finding that water would help bolster the prospects for future human settlement of the Moon, he said.

Within that moonscape, there is also an area informally known as the 'peak of eternal light' -- a ridge between the rims of several craters. It receives sunlight nearly all the time, though no single spot is permanently illuminated.

Landing robotic machinery in an area of nearly continual sunlight helps deal with issues of thermal control and power generation. Therefore, Stooke points out, the peak of eternal light is considered a prime landing target region.

Stooke asked himself: Given that this area on the Moon is a potential target, how do we get to select spots and maximize rover operations?

In his assessment, Stooke took into account four things:

• Good lighting - that is, long periods of sunlight;
• Good view from Earth, a factor that cut out half of the well-lit area;
• Feasible rover routes into craters; and
• Small fresh craters (giving the freshest regolith for samples of South Pole-Aitken basin ejecta (recycled through multiple impacts since then, but still SPA material).

"Add all these factors and you can identify several good landing points, which is what I have tried to do. I'd like to see a mission like this, perhaps as a follow on to the SPA sample return mission," Stooke said.

In utilizing imagery taken in 1994 by the U.S. Pentagon's Clementine spacecraft, Stooke has tagged seven landing zones, areas from which a rover might have access to nearby, permanently shaded terrain.

Several of the spots -- 2, 5 and 7 -- are essentially those once considered by the European Space Agency under the rubric of the now defunct EuroMoon 2000 project.

To best sample SPA rim material, Stooke said, sites are chosen on the ejecta blankets of Shackleton and de Gerlache craters (which cover the whole 'peak'), but adjacent to small craters which will have excavated, fresher material from under the local weathered lunar regolith.

Sites 1 and 2 are on the rim of Shackleton. Both allow rover access to the interior of Shackleton, but its young age may mean its walls are too steep for safe driving and its volatile content may be low. Sites 3, 5 and 6 offer short and easy drives into a nearby crater, but its small size may limit its volatile reservoir potential.

Site 4 offers lengthy -- over 12-miles (20 kilometers) -- drives into a crater that appears to be older than Shackleton, so it may have accumulated more volatiles and have shallower interior slopes. An Earth-Moon radio ink could only be via the lander remaining at site 4 (or relays deployed along the way) as the 'peak' will hide Earth for much of the route.

Site 7 offers several pathways into de Gerlache crater, including a short direct trek if the walls are shallow enough, as well as longer diagonal routes.

In Stooke's view, the set of wished-for landing sites offer access to SPA material and volatiles. Sites 4 and 7 are probably the best for access to volatiles because of the size of the dark areas and the shallower slopes on the rover route.

But there is a caveat to this lunar research. Knowledge of lunar topography is extremely limited in this area because of the effects of shadowing in both Clementine images and Earth-based radar, especially inside craters. So a detailed analysis of route safety and communications is not yet possible, Stooke said.

People have long been interested in the lunar poles, even before the former Soviet Union boosted Sputnik 1 into Earth orbit, Stooke said. As early as 1955, the Soviets were scripting a plan a remote controlled lunar rover at one of the poles, he told SPACE.com .

Furthermore, in 1961, the Nobel Prize winning American cosmochemist, Harold Urey, identified possible ice at the poles as a target for lunar exploration. So the idea is not new, and interest in scouting out polar ice has grown with NASA's Lunar Prospector data that was gathered in 1998-1999.

One thought stemming from Stooke's research is how best to handle Earth-Moon communications.

"It's tricky at the poles because the Moon's axis is tilted about 5 degrees off the Earth-Moon line. So if you're at the pole, Earth is sometimes five degrees above the horizon, which is good. But sometimes it's five degrees below the horizon. Then you have a communications blackout. Periods of no communication would last a bit less than two weeks," Stooke said.

One solution is a relay station at about 85 degrees latitude on the Moon's near side. But Stooke offers another alternative.

"Not perfect but quite good and probably easier in the near term is communication with satellites in geostationary orbit," the researcher points out.

"The geostationary orbit is tilted such that, not all the time but frequently, when Earth is below the polar horizon some geostationary satellites are not. Given suitable radio equipment on a few geostationary satellites, they could cover most of the blackout periods at the Moon's pole. I would fly lunar communication equipment piggyback on satellites normally dedicated to other purposes," Stooke suggests.

"My work is intended to help plan a necessary intermediate step, getting robotic rovers into the area to examine the ice. This is not an active mission, of course, but it could be one soon," Stooke concluded.