For NASA, sending a crewed mission to Mars has been the long-term goal for over two decades. China has joined the club in recent years, with plans to send crewed missions to the red planet ahead of NASA. In both cases, the plans envision a stepping stone approach, using habitats and infrastructure in cis-lunar space to ensure that regular missions can be possible someday. They also envision how regular missions to Mars could lead to permanent habitats on the planet’s surface.