English? Russian? Hindi? Chinese? French? Spanish?
Which language is more important on the Moon?
Well, given English is the only language that has ever been spoken there, I dare say it is the most important there...
But Russian robots are still there and they have insignia in Russian.
http://en.wikipedia.org/wiki/Lunokhod
http://en.wikipedia.org/wiki/Lunokhod
Aren't the Chinese planning a manned moon mission? If so, Chinese is surely destined to be the only language of the moon, since the days of Western manned moon missions is long gone.