I just have to say this, even though I should let it go: the poster who believes that NASA hasn't done jack, and that we should be sending manned missions to Mars by now has exactly no idea of what he's talking about. Incredible baloney. Must be a troll-type comment to mess with people.
I've spent a significant part of my life teaching astronomy, space travel, NASA work, space shuttle, and on and on. I've known the people who have engineered some of our machines, and the person who designed the Hubble Repair mission. This sloppy "NASA should do this, NASA sucks on that" commentary beggars the imagination. Cackalacky's intelligent responses show great actual knowledge; and he too knows that they are just the tip of the iceberg concerning NASA accomplishments and the "ease" of developing such missions. I applaud him. NASA has accomplished so much in terms of space exploration on the crumbs of budget that the politicians deign to provide that the guys should be enshrined as heroes. These are the guys who can aim microscopic [comparatively] orbiter machines so near giant far-distant planets that the gravitational curves they get propel them on EXACTLY to the moons of those planets to take the pictures to the minute.
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Everyone with any knowledge at all about the difficulties of space exploration knows that while planetary robots explorers are do-able on small budgets, manned exploration is not. To have manned exploration, barring some astounding new propulsion breakthrough, it must be staged. First a solidly useful presence in near space --- REAL orbiting habitation with muscular spacecraft-assembly and repair capability [not the puny spacelab/station], Second an orbiting lunar base, with a slow concurrent building of a permanent lunar habitation [maybe even with some mining and refining capability], Third an orbiting manned attempt at Mars [needing all the breakthroughs mentioned by Cackalacky and more], Fourth, several more attempts at Mars to build a permanent orbiting living facility with significant air, water, and food processing in cyclable technologies, Fifth, several missions then to the surface with the orbiting facility as the staging base and the escape hatch when something goes wrong. This stepped procedure would be hugely expensive and very long term. When Bush made some grandstand comments about us going to Mars, the NASA insiders roared with disbelief. NONE of them wanted to hear that political crap. It threatened to get the ignorant Congress and people oriented to a Fool's Errand and suck all funding away from things which we really could do. Thankfully, everyone who is a serious player realizes how full of crap that was, NASAs budget wasn't totally cut to the bone [though it was a near thing], and we can still have marvelous things like Curiosity and deep-space telescopes to actually teach us something.
The usefulness of actual manned landings anywhere is almost zero anyway, unless there would be a permanent scientific/technology base. The concept is almost entirely one of ego and fantasy. Yeh, it was "nice", but Neal Armstrong, in the end, discovered nothing about the Moon. I'm glad that he went, because we need an ego boost once in a while, but if we're ever going to grow up, we should be doing things which allow us to actually learn something. Curiosity sure does that.