Elon Musk fleshed out his vision for establishing the first colony on Mars in a recent interview. As soon as 2018, Musk's SpaceX venture could launch an unmanned spacecraft to the red planet, he said, and that could be followed by future unmanned flights every two years -- timed for when the Earth and Mars orbits position the planets closest together. A cargo route to Mars would need to be established in advance of any manned trip, Musk said, and he compared the supply trips to trains leaving a station at regular intervals.