NASA on Tuesday added more delays to its Artemis moon program, scheduling for 2026 its first astronaut lunar landing in half a century while spacecraft from Elon Musk's SpaceX, Lockheed Martin and other contractors face development challenges. The U.S. space agency's first two Artemis missions involving astronauts were each pushed back nearly a year in delays designed "to give the Artemis teams more time to work through the challenges," NASA administrator Bill Nelson told reporters in a news conference.