Technically, we haven’t had any manned missions to any planets yet. The outer planets, with their high pressures and gaseous compositions that lack a solid surface are unlikely to be entered by humans. Meanwhile the inner planets are, in general, too hostile for us to land on due to their proximity to the Sun – Mercury and Venus are too hot and the pressure on Venus much too high. Only Mars seems to be really within reach and, as a result, this planet has been chosen as something of a happy medium.
Information gathered by previous and current missions has shown Mars to have similar characteristics to our planet. These similarities make Mars the most logical next step when it comes to exploring other worlds. Not only do we think it is feasible to send humans on a flyby mission, but one day we could even walk on Mars’s surface.
Mars is also close to Earth, meaning that astronauts would have to travel no more than 150 to 300 days depending on the speed of launch and alignment of Earth and Mars, making the journey a bit of a safer choice. Of course, even travelling to, let alone landing on, Mars, will prove costly. So imagine just how much more expensive and dangerous going to other planets would be – mankind is not ready for that just yet!