Other than robot probes, which are cost-effective and provide good science and startling images, there will be no manned expeditions beyond the earth-moon system for quite some time, if ever.
The obstacles, ultimately, are not technical - though they are daunting. The intense radiation, long duration of the trip and challenges posed by landing and living on the martian surface are all non-trivial. But with dilligent effort and steady innovation over time these could be overcome and can be considered engineering matters.
No, the real challenge comes from the underlying motivation which is surely not exploration or even adventure in a romantic sense but short-term political gain, pork barrel style fund transfers from the treasury to contractors and *spin-offs* that are almost entirely military in application.
A serious martian expedition would require decades of patient, consistent, international effort. Unprecedented cooperation on a huge scale would be needed. The end result would be permanent habitation (or what's the point?). There is little indication our species has the chops for this sort of work at the moment.
I can imagine a culture that could, patiently and methodically, over centuries, explore, and to whatever extent is possible colonize the solar system. This culture has yet to arise.
So we can safely place this Bush admin announcement in the hot air category.
Oh, I'm sure that work will begin, but it'll be the type of research which employs a few thousand scientists and engineers, produces a few *proof-of-concept* pieces of tech, becomes the subject of a science documentary or two over the years, makes the cover story of *Scientific American* every now and again but mostly fades into obscurity.
What I am much more concerned about and what is much more likely to be seen are orbital weapons platforms carrying nukes, particle emitters and other bits of sky mounted killingry. This could happen within a few years.
DRM