“It is finally getting to the point where we are investing in the capabilities that will get us there in a time frame when people are really beginning to talk about it realistically,” Garver said.

But before that can happen, David Alexander thinks NASA administrators and the nation's leaders need to answer some fundamental questions.

“The biggest issue that a lot of critics are saying is 'why? Where are we going, what are we doing there, and what are we going to do with this big thing we have developed?,'” Alexander said.

As the U.S. Congress struggles with the national debt and how to maintain vital federal programs, it could be tempted to cut funding for a trip to another planet set many years in the future.