The first footsteps on the moon — made by Armstrong on July 20, 1969, on the mission known as Apollo 11— came 3½ years before the last ones. Since then, astronauts have been stuck close to the Earth, mostly circling a few hundred miles overhead in a spacecraft that’s little more than a glorified cargo truck.
So now what?
That question preoccupies NASA and worries the Obama administration. The president said in March that NASA is beset by “a sense of drift.” Even some of the men who once walked on the moon are divided on how to proceed. Options could include going back to the moon, landing on an asteroid, shooting for Mars or even ending human exploration of space altogether.