http://www.slate.com/articles/technology/future_tense/2015/01/should_american_colonists_on_mars_pay_u_s_income_taxes.html

The dream of sending a manned expedition to Mars has long been with us. Yet, despite periodic enthusiasm, it seems we have made little progress. Until now. Our understanding of the planet’s environment (past and present) increases almost daily. Just recently, we tested a rocket ship capable of taking people to Mars. And a surprising number of people would volunteer to go to Mars, even if it meant not returning. (Elon Musk is fond of saying that he would like “to die on Mars, just not on impact.”) As engineering and other hurdles fall, it is time to address one of the most pressing—and yet least discussed—problems facing such a journey, one that could undermine it almost from the beginning.