I currently work for NASA and can say this has been a good conversation for the last couple of months 'ever since Newt proposed a moon colony'. There is no chance of us leaving earth if politicians continue to ignore how big of an impact science is on economic growth. That is it PERIOD, our funding is so very limited and we stress for 100k instruments that HAVE to be on ISS. I envy Neil Tyson for his courage on speaking out about the budget problems (even if only three senators will listen to him when he testifies *New Mexico, Florida, and Texas).
With that said. Let's look at the possibility of Mars being Colonized. I see a lot of you referring to terraforming and the lack of a magnetic field. Both arguments are correct in that they are HUGE questions, but we are unsure of the real outcome of an attempt at creating an atmosphere. It would take a large amount of testing on the surface of Mars to truly know. Right know, we are looking at Mars more as research station similar to a 'Moon Base'. This is not something that should be considered a let down though. If we can create fuel on Mars and draw water from Mars I can not imagine the advancements in space travel.
Just to answer some questions above me: Yes Mars has a magnetic field, very weak but it is there.
If we wait for Earth to be in danger we will be too late. We need to start reaching out now.
Let's just hope that China publicly announces a trip to Mars, we will be on Mars in 2 years. Currently it is funding holding back this nation.