Second, when we land on that planet, we must be prepared to occupy it. I would propose that we land with the intent of leaving behind the first settlement of humans, and the intention to return on a regular basis. This will afford the United States the opportunity to set up the government and administrative tools which will see the United States in the driver's seat in perpetuity. Calling it the 51st state isn't all that far fetched an idea. It would give the government of Mars the ability to make it's own decisions, but would allow it to rely on the Government of the United States for certain services. Mars would in essence become the 51st state.
Further I would recommend that the United States return to the Moon and utilize the same model to occupy and govern that planet. It would become the 52nd state. Once these two bodies have been occupied, it would be time to move on to other planets as feasable.
Before anything else I recommend a Manhattan scale effort to develop an SSTO Space Plane within the shortest amount of time possible. I would actually rank this above the importance of landing on Mars or returning to the Moon. We can develop a program to land on Mars. It would in certain ways resemble the Apolo program. We would see huge boosters, modules' landing craft and an escape vehicle from which our astronauts would leave Mars and reenter space, if it weren't for one caviot. Until we can take off from an airport and fly into space aboard a reuseable vehicle as easily as we can fly from Los Angeles to Washington, D.C., we will never occupy space. And so I must support the development of the SSTO Space plane in advance of any effort to return to the moon or visit other planets.
That space plane should be built within specifications that would a modified version landing and departing other planet surfaces, specificly Mars and the Moon. It should be developed so that modification of the main design would provide a secondary vehicle that would be capable of traversing to Mars in comfort. Once we have a fleet of these planes/spaceships, they can be stationed in space for trips that start at a space station and end on the surface of the Moon or Mars. The first duty of the colonies on the Moon and Mars would be to develop a landing strip for use by the space plane.
Therefore I propose that as part of the plan to land on Mars by the end of the decade, we first develop the SSTO Space Plane. We then use that space plane to help construct and occupy a real space station and partially construct the interplanetary vehicle with which to make that first trip to Mars, from that platform in space.
Look, this is just an outline. Some of it may be unattainable at the moment. Perhaps this plan isn't as air tight as I'd like it. But it is a framework to build on and it's time the United States reclaim some of the bottomless pit welfare state money and put it to good use for a larger part of mankind that it helps out now.
The notion of reusable launch vehicles has huge promise but little backing within NASA. The X-33 program was ambitious and underfunded. It failed in the area of composite tanks but it might have failed elsewhere even with more money. The X-34 solved the composite tank problem, smaller scale, but it was single string in many areas and relied on a Government Furnished Engine(GFE) that was poorly executed. NASA's failure on two Mars probes made them suddenly risk adverse and unwilling to take a chance on the relatively low cost X-34 approach and they cancelled X-34 beacuse the cost of adding redundancy to the avionics systems and likelihood of a further delays in the propulsion system would likely be cost prohibitive.
You nailed the real reason for going to the moon and beyond by citing the explorative nature of the USA. It makes a lot of sense to go to the moon and then beyond. The moon is actually a better space station than the ISS. It gives you a chance to practice things while only three days from the earth as opposed to going to Mars which is at least six months from home. Mars exploration in reality only makes sense when you consider nuclear propulsion, which the greenies are dead against. In fact with two week nights on the moon you need an SP-100 like nuclear generator to make it economically feasible to build a campsite leading to a more permanent lunar infrastructure.
I have long been an advocate of exploring our solar system for my own selfish reasons but we are a long away from having the resolve to do so. My read is that with the war on terrorism that we are farther away than ever.