https://www.newscientist.com/article/mg23831833-000-crewed-missions-to-the-moon-and-mars-need-dreamers-and-doers/

More than three centuries later, this flight of fancy became a reality when Neil Armstrong took one small step. “It suddenly struck me that that tiny pea, pretty and blue, was the Earth,” he later said.

Since then, we have come crashing back down to our little blue world. Although the International Space Station has been a success in low Earth orbit, the changing political winds have left NASA struggling to get any crewed deep-space missions off the ground. As presidents have come and gone, the agency has spent decades flipping between prioritising a pioneering trip to Mars or a return to the moon (see “Team moon vs team Mars: the battle over the future of NASA”).