....Why do you think it would take a manned spaceship longs to get to Mars than an unmanned one? I'm sure they would do everything possible to make it as quick as possible. This way they wouldn't have to worry about having extra food and resources.
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Because the orbits of the two planets have to line up in a way that makes it a short trip. A short trip "coming AND going" isn't going to happen.
Face it, round trip to Mars is four years or longer.