The multibillion-dollar series of missions aims to return astronauts to the moon's surface by 2028 before China and establish a long-term US presence there over the next decade, building a moon base that would serve as a proving ground for potential future missions to Mars The four astronauts of NASA's Artemis II mission entered the moon's gravitational sphere of influence early Monday morning as they cruised along a path that will soon take them over the shadowed, lunar far side to become the farthest-flying humans in... [3570 chars]