"You want a launch vehicle today that will service the ISS? We've got it sitting down there," Cernan added, referring to the Space Shuttle. "So before we put it in a museum, let's make use of it. It's in the prime of its life, how could we just put it away?"

The Space Shuttle was cancelled in 2004 by President George Bush a move that never looked likely to be reversed by his successor Barack Obama given the state of US finances. Part of the problem has been agreeing on the goal of space exploration, with opinions divided on a return to the moon, a more ambitious journey to Mars and deep-space scientific exploration using probes.

Poignantly, only a fortnight ago NASA published the landing sites reached by Armstrong and Cernan on their extraordinary missions. Increasingly, the impression is of a bold period in history that could take humanity decades to live down as it tries to match its achievements.