The last time U.S. astronauts landed on the moon was 11 December 1972, in an act of exploratory courage avoided for the next thirty-nine years. That era's space travelers didn't stay very long, and by all appearances the next trip won't be for a long time to come.
Why bother to go at all? Are there too few earthbound problems, so that explorers need to go to the moon to find more? These are questions people have asked since the very first attempts to put people into space, and there are better answers now than ever before.
Humanity needs a moon base. This is not some Martin Landau-led "Moonbase Alpha," either; there is real human and commercial value to be developed by living and working on the moon. It is more than sentimentality that compels explorers to search the next valley and beyond the next mountain.
Humanity does one thing really well: it spreads itself into all available land. In so doing, it expands both its grasp and its need for new horizons. People, in short, need to know what is "out there," and exploration from a moon base is not only easier in terms of gravity-well escape, but also highly remunerative if the moon happens to return several trillion dollars' worth of raw ores for manufacturing and construction.
As explorers, it seems high time to reach out into the solar system. Humans must someday establish human outposts in places other than Earth, both to satisfy exploratory wanderlust and to protect Earth's inhabitants against the probability that something like Shoemaker-Levy 9 will someday not be captured by Jupiter's gravity, putting Earth at risk for another extinction-level event.
The National Aeronautics and Space Administration has announced tentative plans to return to the moon. As is common with NASA, those plans seem, in the eyes of impatient observers, to include a hundred years of planning, ten years of building, and fifteen minutes of exploratory victory. They want to be careful, which is a laudable goal, and it is possible that the plans already in the works will be carried out in part by 2020.
"In part" is a reference to the multi-phase character of NASA's plans. First on their list, of course, is to find a place to land. They want this to be near one of the poles due to the increased likelihood that usable water in life-supporting quantity is available. The recent LCROSS mission may have aided in the search for this crucial compound.
Next, the Agency plans to look for other natural resources in and under the soil. These include metals, minerals, and, very likely, a substance already known to exist there, molecular hydrogen. Some of these materials will be useful for building or for life support; hydrogen in sufficient quantity goes directly to the production of rocket fuel. Find enough, and you can save billions of dollars by not having to transport as much raw material from the deep gravity well surrounding Earth.
If our hardy astronauts/colonists are to live long enough to send others on to Mars, the landing site must be safe for repeated landings by heavy transfer craft. Presumably, this will be accomplished by robotic workers (think Mars rovers, not "I, Robot") that will put the foundations in place and wait for humans to finish and fine-tune the site.
How long will this take? If NASA really intends to push all of this development, flight, assembly, and construction to 2020, it will be easily 2030 before men and women walk into a habitat ready for long-term stays. These habitats will require some sub-surface preparation, similar at first to mining operations; and facilities must be created to supply power, provide transport, and seal off living quarters from the hard radiation of space. Remember, the moon has no protective atmosphere, and human crew will need to spend most of their time in-doors, most likely below ground.
This preparation is, NASA says, to be done by four-person crews who land, spend seven days onsite, and then return to Earth. Whatever work can then be done by remote- or AI-controlled robots will proceed as before, while the next mission team gets ready to deploy to the moon.
Maybe one of the original astronauts who walked on the moon will still be alive when these excavations and assemblies begin. It's possible. What is certain is that humanity has lost nearly forty years, and it is time to saddle up and take renewed interest in the future. The moon, Mars, and the solar system await our development.