Astronauts and technicians working and living at Lagrange points will develop the technologies needed to change the Mars mission from a visit into a colony. There is immediate, profitable work to be done at L2. Industry and people will always follow profits, and in this case civilization benefits enormously.
Why future astronauts may be sent to 'gravity holes' - space - 29 August 2009 - New Scientist:
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Lagrange, or Lagrangian, points are great swathes of space where the gravitational acceleration from the Earth and the sun are exactly equal, letting objects stick there with very little effort.
Because they're far from warm stars and planets, they make useful havens for ultra-cold telescopes that measure fluctuations in the temperature of deep space.
The Wilkinson Microwave Anisotropy Probe (WMAP), which measures radiation from the big bang, lives at a Lagrange point called L2 more than 1 million kilometres away. The successor to the Hubble Space Telescope, the massive James Webb Space Telescope, will also be sent to the spot, which lies in line with the sun and Earth . . .
. . .But what would humans do there? One useful task is repairing and upgrading the new telescopes, like astronauts have done five times with Hubble.
"Hubble is probably the most productive scientific facility ever developed in the history of science, and it's largely because every four or five years, we take out the old instruments ... and go up with brand-new instruments that address different questions and embrace the latest technology," Lester says. "If we want to have humans having anything to do with these new telescopes, we really have to think about Lagrange points."
. . .It takes surprisingly little energy to travel between these points. That's because massive bodies like the sun and planets have gravitational fields that resemble mountains and hills, but Lagrange points are all at gravitational lowlands. Once set on the right path, spacecraft can coast along the gravitational contours of space between these lowlands, as if travelling on an interplanetary superhighway.
"Going back and forth between Earth-sun Lagrange points and Earth-moon Lagrange points is pretty much a matter of giving the thing a swift kick," Lester told New Scientist.
Future astronauts could repair telescopes at a staging area at the nearest Earth-moon Lagrange point and send them sailing back to L2 when they're done. They could also assemble large telescopes or spaceships at the staging area and then send them out to farther-flung destinations.
. . .Others see Lagrange points as stepping stones on the way to places like Mars.
"It's a convenient crossroads on the way to a place you really want to visit," says Lou Friedman, founder and executive director of the Planetary Society, a space advocacy group that supports sending astronauts to Mars.
"The place we all want to go is Mars. Stepping out into interplanetary space, Lagrange points present the nearest milestone to Earth that's still beyond the moon," Friedman told New Scientist.
Going to L2 would take about a month and communications from Earth would take about four seconds to arrive at L2, while a trip to Mars would take at least six months and would involve communications delays of about 20 minutes."
L5 Society - Wikipedia, the free encyclopedia:
"The name comes from the L4 and L5 Lagrangian points in the Earth-Moon system proposed as locations for the huge rotating space habitats that Dr. O'Neill envisioned. L4 and L5 are points of stable gravitational equilibrium located along the path of the moon's orbit, 60 degrees ahead or behind it.
An object placed in orbit around L5 (or L4) will remain there indefinitely without having to expend fuel to keep its position, whereas an object placed at L1, L2 or L3 (all points of unstable equilibrium) may have to expend fuel if it drifts off the point."
