re: caves and language subtleties
In the 50's or even early 60's, there were many theories!
But caves don't exist as their existence seems far more related to water than we thought before; Also, the Moon is constantly bombarded by micrometeorites that level the ground, filling up any exisiting hole.
Years ago, when the first moonlandings took place, we talked about alunissage (moonlanding), as opposed to atterrissage (earthlanding). It seemed quite sexy and nobody fussed.
But then, Mars, Venus, Mercury came into mind..Amarsissage, Venusissage, Mercurissage..!!Ouch, too much, it was too much to bear!
So, it was decided to drop "alunissage" and keep "atterrissage" for all the planets.
Raoul