The National Research Council has reviewed NASA's plans to explore Mars and concluded it won't work.
From the Washington Post:
"The report makes a case for sending astronauts back to the moon. That had been a key element of NASA’s strategy under President George W. Bush. But President Obama and his advisers explicitly opposed another moon landing (“I just have to say pretty bluntly here: We’ve been there before,” Obama said in a speech on space policy in 2010)."