A crewed mission to Mars faces problems that robotic probes never had to solve, and Hank Green walks through what they are. The trip itself takes months each way, exposing astronauts to radiation levels far above what NASA considers safe on Earth, with no magnetosphere or thick atmosphere to shield them once they leave orbit. Green covers the psychological strain of that kind of isolation too, pointing to the Mars Society's Mars Desert Research Station and NASA-backed mock missions, where crews sealed away for extended stretches show real fatigue and irritability by the end. He also gets into the engineering side, including NASA's Space Launch System, built to haul the fuel, supplies, and hardware a Mars trip would actually require. Green weighs these obstacles against the scientific case for going anyway, the data only a human crew could gather about the planet's surface and resources. The episode closes with a personal touch: a recorded message from Green's 17-year-old self, checking in on whether Mars ever happened.