"Here men from the planet Earth first set foot on the moon, July 1969 A.D. We came in peace for all mankind." --- from a plaque marking the spot on the moon where the historic event took place.
Sorry, but no one (or alien) is going to know what "A.D." means when they read this in the distant future. In fact, they will most likely not know English, what a 'foot' is nor be able to guess the meaning of 'peace.' Especially if they're from the far side of the moon.
Note one man's disenchantment: "Astronauts . . . submit to the severest bodily ordeals in order to satisfy the ritual demands for space travel to distant parts of the solar system. To a certain degree, vicarious participation in these rites by the earthbound inhabitants of the planet, made possible through film, television and radio, restores the waning sense of high adventure; and the ever present possiblity of death in a cosmic stting augments, as in motor racing, the daily dose of untrammeled gladiatorial violence faithfully provided by the mass media." Lewis Mumford in The Pentagon of Power: The Myth of the Machine, 1970.
The antiquated shuttle program has reached its final frontier and paid dearly for it. America doesn't need any more dead heroes at the moment.