Honestly I think getting someone to Mars and back at this point is an engineering problem in that: 1. Humans can live in space for extended periods (eg the ISS

Honestly I think getting someone to Mars and back at this point is an engineering problem in that: 1. Humans can live in space for extended periods (eg the ISS); 2. We have the capability to land something on Mars and take off again, rendezvouzing with an orbiting spacecraft. We did this on the Moon; 3. We have the capability of getting enough fuel and payload into orbit and then sending that to Mars and back. Now this part is tricky because every pound of payload you need has a knock on effect in terms of more fuel needed plus more fuel to carry that fuel. This I think is actually the trickiest part but largely comes down to a function of launch costs. That all being said, it looks like it'll cost hundreds of billions of dollars and be an active mission for ~2 years. Is it worth it? That's a reasonable question to ask given how many unmanned probes we could send for that same money and what the value is of sending a meat bag to another world. Now colonization is a whole other beast. My definition of colonization is that the colony is self-sufficient. For this, IMHO we simply don't have the technology. Far from it. Too much of what we rely on is provided "free" by the Earth. Air, water, plants and animals. Resource extraction is ludicrously cheap compared to anything in space or on another world. But think about the daily things you need: clothes, food, computers, shelter, transport. There's a complex web of dependencies on any one of these things such that a good portion of the world is needed and a pretty significant number of people are required. Also, does Mars even make sense? It has almost zero atmosphere. I've read that Mercury may in fact make much more sense. For one it'll solve the energy problem (solar on Mercury, anyone?). Not that living on Mercury is without problems of course.