Alan Bean says of "A Window on the End of an Era":

The Apollo 17 crew, Gene Cernan, Ron Evans and Jack Schmitt, are busy configuring their spacecraft for TransEarth Injection - a burn that will rocket them out of lunar orbit and on a trajectory safely back to Planet Earth. If they had the time to look out the window they might see what we see - the stark lifeless beauty of the Crater Leuschner bathed in a beautiful, blue-tinted, reflected earthlight, with the magnificent blue-and-white Earth appearing to slip behind the lunar horizon for the last time. But they don't. Their focus is inside.

It is about 5 pm at Mission Control in Houston, Texas on December 16, 1972, where we were in the final phase of completing the boldest era of exploration in history. The Apollo 17 crew's mantra had been "the end of the beginning." Apollo had done its work, taking humans 240,000 miles from the shores of our home planet, and setting the stage for future exploration.

But since this last glimpse in 1972, nobody has ventured further than 400 miles from earth. Few of us realized humans would not return to the Moon to stay for a very, very long time. But when they do, it will be on the shoulders of Apollo.

The gift of the Apollo generation is the certainty that voyages into space to distant worlds can be safely done. However, it must be left to future generations to take the next step. They have the way right now, but it will be done only when they have the will.

I know that someday a new energy and quest for exploration will emerge from the leaders of our great nation, to reach again for the Moon and beyond - goals technically within our grasp but not yet captured by their spirit. As we witness the Earth set on this last orbit of the Moon by humans, Apollo's place in history was complete: Our work as the new explorers was done, and it was time to pass the torch to others to fulfill the promise of Apollo.