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)."

http://www.washingtonpost.com/national/health-science/nrc-human-spaceflight-report-says-nasa-strategy-cant-get-humans-to-mars/2014/06/04/e6e6060c-ebd6-11e3-9f5c-9075d5508f0a_story.html