Hey just because it seems difficult or insurmountable to us now does not mean that it is impossible or that we can't do it at sometime in the future.
No. But we can't even see a way to "get there from here."
At our current level of technology, we have exactly the same chance of creating a self-sustaining colony on Mars via spaceship transport as we have through astral projection. (We can't even create a self-sustaining colony in low Earth orbit, in case you hadn't noticed.)
At our current level of technology, we have exactly the same chance of creating a viable enclosed habit as we do of being able to survive without food, water, and air via chi projection. (Do you remember the Biosphere fiasco?)
And even at any level of technology we can realistically expect in the foreseeable future, those chances will remain identically zero.
We are at least one major breakthrough away from any chance of succeeding. Oddly enough, we're also "at least one major breakthrough" away from warp drive, from resurrection upon demand, from human-level artificial intelligence, from teleportation, and from cheap matter replication. In fact, any of those
might provide us with the necessary technology to be able to successfully colonize Mars. But spending money and effort now on an extra-terrestrial colony instead of on building the necessary technological infrastructure
to make it possible is simply pouring money and effort away.
Mars colonization is the modern equivalent of a cargo cult. We have a romanticized idea of what is supposed to happen, but no possibility at all of actually making it happen. No matter how hard the Polynesians worked on making perfect models of runways and radio shacks, what they build would never work as an airfield. And the more time and effort they spend on building bamboo radio antennae, the less they're spending on learning science, technology, engineering, and such that would let them even understand why bamboo doesn't work for an antenna.
The metaphor of 16th-century colonialism is often brought up. Unfortunately, it's a false metaphor. Columbus
had the technology he needed to sail the ocean, more or less at will. He had the technology he needed to survive in
terra incognita for a more or less unlimited amount of time. He had the technology he needed to work with the lands that he found, to build buildings, farm crops, and so forth.
What would you have told a 16th-century explorer who wanted to take his wooden sailing ship to the moon? "Just because it seems difficult or insurmountable to us now does not mean that it is impossible?" I'm sorry, but sailing a 16-th century ship to the moon is, in fact, impossible? "We can do it at sometime in the future?" Sure -- but what technologies would he be researching to make it possible? Better sails? A more reliable magnetic compass? A deeper keel to keep the ship from foundering? Our explorer couldn't even imagine the technologies that would be needed to "sail" to the moon.
We will
eventually be able to colonize Mars. But the tools and technologies we use will no more be an extension of our current space technology than a Saturn V was an extension of the
Santa Maria.