So often I see shows on TV discussing the seemingly inevitable terraforming of Mars by humans. These shows generally talk about the challenges in creating an atmosphere (basically, heating up the frozen carbon dioxide to release greenhouse gases), thereafter releasing all of Mars' water, and eventually oxygen. However, from my reading I thought it was generally believed that Mars' small size and limited gravity made it very difficult for it to hold onto an atmosphere. If this is true, then why would we even waste time creating an atmosphere at all? Wouldn't it just be a waste of time? Secondly, Mars has no magnetic field to protect it from solar flares and CME's and from cosmic rays and other sources of radiation from outer space. This point is always glossed over by popular science shows as a "minor" hurdle. However, it seems major to me. Therefore, my second question is whether it is possible to artificially generate a magnetic field big enough to protect an entire planet the size of Mars. If so, how might one generate such a field? Is it even possible?