Even as it leads the partnership assembling a new Earth-orbiting space station, NASA is looking to more distant vistas. Possible destinations include the moon, visited by Apollo astronauts between 1969 and 1972; an asteroid; or a solar orbit nearly a million miles away that would serve as the site for a powerful new space telescope. But especially, Mars is a target. “Mars continues to be the grand goal,” said Bret Drake, who leads mission planning activities at NASA’s Johnson Space Center.