You look up at the night sky and watch a tiny dot moving across, it can't be a bird, or a plane, way too small and too far away. “Could that be a satellite? Did I just watch a UFO?” You ponder, nope. In all probability, what you just saw was the International Space Station—the grandest and most expensive construction project ever attempted by humanity.

Charles Bolden, a former space shuttle commander and National Aeronautics and Space Administration (NASA) Administrator from 2009 to 2017, dreamed of being the first person on Mars when he first checked in for astronaut training in 1980. At the time, NASA thought that a crewed Mars mission was thirty years away. Of course, we know now that prediction was overly optimistic. Yet there have been technological advancements and a renewed interest in human exploration of the Red Planet in the past few years. How soon could a Mars mission be possible, and what technology will NASA need to make it a reality?