After decades of watching astronauts circle Earth, space visionaries finally have reason for optimism: NASA and other agencies are working with the White House on a bold, new course of exploration. Whether the destination is the moon or Mars — or whether any plan actually makes liftoff — remains to be seen. For space buffs, just to get a defined mission would be cause for hope. “Put it this way: I think we have to continue to move forward and, at least with the discussion that’s going on, that’s good,” said Everett Gibson, a NASA scientist who studied moon rocks from the Apollo astronauts and the Mars meteorite that may hold evidence of past life on the red planet.