From inside SpaceX's rocket factory, Gordon-Levitt asks Musk if he thinks a Mars landing is possibly in the 21st century.
"I think it's realistic. I think it's extremely difficult," Musk said. "The question is how far can SpaceX advance that cause. The goal of SpaceX is to revolutionize space travel. The long-term goal is to establish Mars as a self-sustaining civilization as well as to just kind of have a more exciting future."