Space.com gives us "10 Reasons to Put Humans Back on the Moon." While some of these reasons seem obvious, like our needs for dreams or a common goal for nations to collaborate, some are less expected, like generating energy from lunar power station.
The original article is spread over ten pages, so here is the full list on one page for your convenience.
Satisfy the soul
Robots could do the job better than human beings, but exploration seems to be in our genes. As said Sir Martin Rees, one of the world's leading theoretical astrophysicists, ""Indeed as a scientist I see little purpose in sending people into space at all. But as a human being, I'm nonetheless an enthusiast for space exploration -- to the Moon, to Mars and even beyond -- as a long-range adventure for (at least a few) humans."
Bring nations together
Just as the International Space Station packed explorers from previously antagonistic nations into tight quarters, an effort to return to the Moon could bring nations together in an era of increasing international tension, some analysts say.
Foster commercialization
Many experts think space tourism and even certain mining and manufacturing will succeed in space if only entrepreneurs are turned loose (and perhaps assisted with federal money or incentives).
[For more information on space tourism, you can read a former post, "Countdown for Rocket Planes."]
The telephone conversation is, by its very nature, reactive, not reflective. Immediacy is its prime virtue. The immediacy delivers quick company, instant stimulation; the stimulation is cathartic; catharsis pushes back anxiety; into open space flows the kind of thought generated by electric return. The letter, written in absorbed solitude, is an act of faith; it assumes the presence of humanity; world and self are generated from within; loneliness is courted, not feared. To write a letter is to be alone with my thoughts in the conjured presence of another person. I keep myself imaginative company. I occupy the empty room. I alone infuse the silence.
—Vivian Gornick (b. 1935)
Gather rocks
"We are talking about finding material from the very early Earth," says John Armstrong of the University of Washington in Seattle. "Samples of the Earth 3.9 to 4.0 billion years ago could tell us a lot about the state of the early atmosphere, what the crust and surface were like, and possibly even when life began to evolve."
Study catastrophe
Studying Moon craters up close would allow scientist to figure out if mass extinctions on Earth, including the death of dinosaurs that allowed the rise of mammals, were the result of single, large asteroid impacts, flurries of smaller assaults, or neither.
Look outward
Astronomers would love to set up observatories on the Moon. Optical telescopes could be placed almost anywhere on the lunar surface and, since there's almost no atmosphere to scatter light, they'd get clear, Hubble-like views of the cosmos.
Generate power
Space if full of free solar power. There are no clouds on the Moon. Those two facts make setting up a lunar power station sensible in the minds of some futurists. The power could be beamed to Earth or to satellites for distribution around the world.
Launch industry
Play is a major avenue for learning to manage anxiety. It gives the child a safe space where she can experiment at will, suspending the rules and constraints of physical and social reality. In play, the child becomes master rather than subject.... Play allows the child to transcend passivity and to become the active doer of what happens around her.
—Alicia F. Lieberman (20th century)
The Moon has minerals, and many proponents of human space exploration figure lunar mining is good enough reason to go back. Gaining experience and mastering the necessary technology might then allow venturous and potentially more lucrative claims to be laid on asteroids, which are rich in metals.
[For more information on the subject, you can read a former post, "Is Space Mining Feasible?"]
Improve technology
No one knows what might be invented in an effort to set up lunar colonies, reach Mars or mine for metals on an asteroid. But a lot of scientists think it's worth finding out.
Stepping stone to Mars
Specialists seem divided on this one. Some think it could delay exploration of Mars or asteroids, while others think it would be a bonus.
Source: Robert Roy Britt, Space.com, December 8, 2003.