NASA have plans for a manned Mars expedition based on the Ares spacecraft they're developing as a replacement for the Space Shuttle. Price estimates vary from $20Bn (presumably for a single round-trip) to $450Bn (presumably for a single round trip plus all the externalities, like developing the spacecraft and equipment and conducting a thorough prior reconnaissance using unmanned landers).
Either way, the direct costs of the Iraq war exceed the maximum cost estimate for a manned Mars expedition, infrastructure and all, by 20%. If we take $20Bn as the cost per mission and $450Bn as the cost to develop the technology to go there, the direct cost of the Iraq war would be sufficient to develop a gold-plated Mars expeditionary capability and send six crews of astronauts to Mars (and bring them back afterwards).
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