Board Thread:Suggestions/@comment-27794543-20190508014010/@comment-4801337-20190604050201

So, actually after rewatching the Josie scene that made us think Sanctum is the moon, I'm more convinced that it's actually just the settlement. Here's how the scene goes:

Russell : We're building a sanctuary for the human race here... Josie: I think I have a name for this place. Russell: I think Alpha is tough to beat. Josie: The latin-root for sanctuary - "Sanctum."

So, based on this, I think Sanctum only applies to the sanctuary (settlement) they were building; not the moon. It's possible that before Josie's suggestion, they intended to just call the sanctuary "Alpha" after their mission team.