A half-century after the first astronauts walked on the Moon, NASA is working on plans for the next round of lunar exploration. A key part of its plans is Gateway, a small space station that would follow an elongated orbit around the Moon. The Space Agency says astronauts would observe the Moon, remotely operate robotic missions, and perhaps stage their own landings from the outpost. This artist's concept shows one possible configuration for the craft. [Northrop Grumman]